diff --git a/apps/cli/README.md b/apps/cli/README.md
index a7b9393..9002c93 100644
--- a/apps/cli/README.md
+++ b/apps/cli/README.md
@@ -1,6 +1,6 @@
-# pisa-cli
+# pisa_cli
 
-`pisa-cli` is a command line interface to interact with the PISA server, written in Python3.
+`pisa_cli` is a command line interface to interact with the PISA server, written in Python3.
 
 ## Dependencies
 Refer to [DEPENDENCIES.md](DEPENDENCIES.md)
@@ -11,7 +11,7 @@ Refer to [INSTALL.md](INSTALL.md)
 
 ## Usage
 
-	python pisa-cli.py [global options] command [command options] [arguments]
+	python pisa_cli.py [global options] command [command options] [arguments]
 	
 #### Global options
 
@@ -54,7 +54,7 @@ The API will return a `text/plain` HTTP response code `200/OK` if the appointmen
 
 #### Usage
 
-	python pisa-cli add_appointment [command options] <appointment>/<path_to_appointment_file>
+	python pisa_cli add_appointment [command options] <appointment>/<path_to_appointment_file>
 	
 if `-f, --file` **is** specified, then the command expects a path to a json file instead of a json encoded
 	string as parameter.
@@ -100,7 +100,7 @@ if `-f, --file` **is** specified, then the command expects a path to a json file
 	
 #### Usage
 
-	python pisa-cli get_appointment <appointment_locator>
+	python pisa_cli get_appointment <appointment_locator>
 	
 
 	
@@ -109,18 +109,18 @@ if `-f, --file` **is** specified, then the command expects a path to a json file
 Shows the list of commands or help about how to run a specific command.
 
 #### Usage
-	python pisa-cli help
+	python pisa_cli help
 	
 or
 
-	python pisa-cli help command
+	python pisa_cli help command
 
 ## Example
 
 1. Generate a new dummy appointment. **Note:** this appointment will never be fulfilled (it will eventually expire) since it does not corresopond to a valid transaction. However it can be used to interact with the PISA API.
 
     ```
-    python pisa-cli.py generate_dummy_appointment
+    python pisa_cli.py generate_dummy_appointment
     ```
 
     That will create a json file that follows the appointment data structure filled with dummy data and store it in   `dummy_appointment_data.json`.
@@ -128,7 +128,7 @@ or
 2. Send the appointment to the PISA API. Which will then start monitoring for matching transactions.
 
     ```
-    python pisa-cli.py add_appointment -f dummy_appointment_data.json
+    python pisa_cli.py add_appointment -f dummy_appointment_data.json
     ```
 
     This returns a appointment locator that can be used to get updates about this appointment from PISA.
@@ -136,9 +136,9 @@ or
 3. Test that PISA is still watching the appointment by replacing the appointment locator received into the following command:
 
     ```
-    python pisa-cli.py get_appointment <appointment_locator>
+    python pisa_cli.py get_appointment <appointment_locator>
     ```
 
 ## PISA API	
 
-If you wish to read about the underlying API, and how to write your own tool to interact with it, refer to [PISA-API.md](PISA-API.md)
\ No newline at end of file
+If you wish to read about the underlying API, and how to write your own tool to interact with it, refer to [PISA-API.md](PISA-API.md)
diff --git a/apps/cli/pisa_cli.py b/apps/cli/pisa_cli.py
index 0f2eb92..440860d 100644
--- a/apps/cli/pisa_cli.py
+++ b/apps/cli/pisa_cli.py
@@ -9,8 +9,8 @@ from getopt import getopt, GetoptError
 from requests import ConnectTimeout, ConnectionError
 from uuid import uuid4
 
-from apps.cli.blob import Blob
 from apps.cli.help import help_add_appointment, help_get_appointment
+from apps.cli.blob import Blob
 from apps.cli import (
     DEFAULT_PISA_API_SERVER,
     DEFAULT_PISA_API_PORT,
@@ -22,9 +22,8 @@ from apps.cli import (
 
 from common.logger import Logger
 from common.appointment import Appointment
-from common.constants import LOCATOR_LEN_HEX
 from common.cryptographer import Cryptographer
-from common.tools import check_sha256_hex_format
+from common.tools import check_sha256_hex_format, compute_locator
 
 
 HTTP_OK = 200
@@ -46,11 +45,13 @@ def generate_dummy_appointment():
         "to_self_delay": 20,
     }
 
-    print("Generating dummy appointment data:" "\n\n" + json.dumps(dummy_appointment_data, indent=4, sort_keys=True))
+    logger.info(
+        "Generating dummy appointment data:" "\n\n" + json.dumps(dummy_appointment_data, indent=4, sort_keys=True)
+    )
 
     json.dump(dummy_appointment_data, open("dummy_appointment_data.json", "w"))
 
-    print("\nData stored in dummy_appointment_data.json")
+    logger.info("\nData stored in dummy_appointment_data.json")
 
 
 # Loads and returns Pisa keys from disk
@@ -61,11 +62,12 @@ def load_key_file_data(file_name):
         return key
 
     except FileNotFoundError:
-        raise FileNotFoundError("File not found.")
+        logger.error("Client's key file not found. Please check your settings.")
+        return False
 
-
-def compute_locator(tx_id):
-    return tx_id[:LOCATOR_LEN_HEX]
+    except IOError as e:
+        logger.error("I/O error({}): {}".format(e.errno, e.strerror))
+        return False
 
 
 # Makes sure that the folder APPOINTMENTS_FOLDER_NAME exists, then saves the appointment and signature in it.
@@ -85,12 +87,81 @@ def save_signed_appointment(appointment, signature):
 
 
 def add_appointment(args):
-    appointment_data = None
+    # Get appointment data from user.
+    appointment_data = parse_add_appointment_args(args)
+
+    if appointment_data is None:
+        logger.error("The provided appointment JSON is empty")
+        return False
+
+    valid_txid = check_sha256_hex_format(appointment_data.get("tx_id"))
+
+    if not valid_txid:
+        logger.error("The provided txid is not valid")
+        return False
+
+    tx_id = appointment_data.get("tx_id")
+    tx = appointment_data.get("tx")
+
+    if None not in [tx_id, tx]:
+        appointment_data["locator"] = compute_locator(tx_id)
+        appointment_data["encrypted_blob"] = Cryptographer.encrypt(Blob(tx), tx_id)
+
+    else:
+        logger.error("Appointment data is missing some fields.")
+        return False
+
+    appointment = Appointment.from_dict(appointment_data)
+
+    signature = get_appointment_signature(appointment)
+    hex_pk_der = get_pk()
+
+    if not (appointment and signature and hex_pk_der):
+        return False
+
+    data = {"appointment": appointment.to_dict(), "signature": signature, "public_key": hex_pk_der.decode("utf-8")}
+
+    appointment_json = json.dumps(data, sort_keys=True, separators=(",", ":"))
+
+    # Send appointment to the server.
+    add_appointment_endpoint = "http://{}:{}".format(pisa_api_server, pisa_api_port)
+    response_json = post_data_to_add_appointment_endpoint(add_appointment_endpoint, appointment_json)
+
+    if response_json is None:
+        return False
+
+    signature = response_json.get("signature")
+    # Check that the server signed the appointment as it should.
+    if signature is None:
+        logger.error("The response does not contain the signature of the appointment.")
+        return False
+
+    valid = check_signature(signature, appointment)
+
+    if not valid:
+        logger.error("The returned appointment's signature is invalid")
+        return False
+
+    logger.info("Appointment accepted and signed by Pisa")
+    # all good, store appointment and signature
+    try:
+        save_signed_appointment(appointment.to_dict(), signature)
+
+    except OSError as e:
+        logger.error("There was an error while saving the appointment", error=e)
+        return False
+
+    return True
+
+
+# Parse arguments passed to add_appointment and handle them accordingly.
+# Returns appointment data.
+def parse_add_appointment_args(args):
     use_help = "Use 'help add_appointment' for help of how to use the command"
 
     if not args:
         logger.error("No appointment data provided. " + use_help)
-        return False
+        return None
 
     arg_opt = args.pop(0)
 
@@ -102,7 +173,7 @@ def add_appointment(args):
             fin = args.pop(0)
             if not os.path.isfile(fin):
                 logger.error("Can't find file", filename=fin)
-                return False
+                return None
 
             try:
                 with open(fin) as f:
@@ -110,63 +181,19 @@ def add_appointment(args):
 
             except IOError as e:
                 logger.error("I/O error", errno=e.errno, error=e.strerror)
-                return False
+                return None
         else:
             appointment_data = json.loads(arg_opt)
 
     except json.JSONDecodeError:
         logger.error("Non-JSON encoded data provided as appointment. " + use_help)
-        return False
+        return None
 
-    if not appointment_data:
-        logger.error("The provided JSON is empty")
-        return False
+    return appointment_data
 
-    valid_locator = check_sha256_hex_format(appointment_data.get("tx_id"))
-
-    if not valid_locator:
-        logger.error("The provided locator is not valid")
-        return False
-
-    add_appointment_endpoint = "http://{}:{}".format(pisa_api_server, pisa_api_port)
-    appointment = Appointment.from_dict(appointment_data)
-
-    try:
-        sk_der = load_key_file_data(CLI_PRIVATE_KEY)
-        cli_sk = Cryptographer.load_private_key_der(sk_der)
-
-    except ValueError:
-        logger.error("Failed to deserialize the public key. It might be in an unsupported format")
-        return False
-
-    except FileNotFoundError:
-        logger.error("Client's private key file not found. Please check your settings")
-        return False
-
-    except IOError as e:
-        logger.error("I/O error", errno=e.errno, error=e.strerror)
-        return False
-
-    signature = Cryptographer.sign(appointment.serialize(), cli_sk)
-
-    try:
-        cli_pk_der = load_key_file_data(CLI_PUBLIC_KEY)
-        hex_pk_der = binascii.hexlify(cli_pk_der)
-
-    except FileNotFoundError:
-        logger.error("Client's public key file not found. Please check your settings")
-        return False
-
-    except IOError as e:
-        logger.error("I/O error", errno=e.errno, error=e.strerror)
-        return False
-
-    # FIXME: Exceptions for hexlify need to be covered
-
-    data = {"appointment": appointment, "signature": signature, "public_key": hex_pk_der.decode("utf-8")}
-
-    appointment_json = json.dumps(data, sort_keys=True, separators=(",", ":"))
 
+# Sends appointment data to add_appointment endpoint to be processed by the server.
+def post_data_to_add_appointment_endpoint(add_appointment_endpoint, appointment_json):
     logger.info("Sending appointment to PISA")
 
     try:
@@ -176,15 +203,15 @@ def add_appointment(args):
 
     except json.JSONDecodeError:
         logger.error("The response was not valid JSON")
-        return False
+        return None
 
     except ConnectTimeout:
         logger.error("Can't connect to pisa API. Connection timeout")
-        return False
+        return None
 
     except ConnectionError:
         logger.error("Can't connect to pisa API. Server cannot be reached")
-        return False
+        return None
 
     if r.status_code != HTTP_OK:
         if "error" not in response_json:
@@ -196,14 +223,17 @@ def add_appointment(args):
                 status_code=r.status_code,
                 description=error,
             )
-        return False
+        return None
 
     if "signature" not in response_json:
         logger.error("The response does not contain the signature of the appointment")
-        return False
+        return None
 
-    signature = response_json["signature"]
-    # verify that the returned signature is valid
+    return response_json
+
+
+# Verify that the signature returned from the watchtower is valid.
+def check_signature(signature, appointment):
     try:
         pisa_pk_der = load_key_file_data(PISA_PUBLIC_KEY)
         pisa_pk = Cryptographer.load_public_key_der(pisa_pk_der)
@@ -212,7 +242,7 @@ def add_appointment(args):
             logger.error("Failed to deserialize the public key. It might be in an unsupported format")
             return False
 
-        is_sig_valid = Cryptographer.verify(appointment.serialize(), signature, pisa_pk)
+        return Cryptographer.verify(appointment.serialize(), signature, pisa_pk)
 
     except FileNotFoundError:
         logger.error("Pisa's public key file not found. Please check your settings")
@@ -222,21 +252,6 @@ def add_appointment(args):
         logger.error("I/O error", errno=e.errno, error=e.strerror)
         return False
 
-    if not is_sig_valid:
-        logger.error("The returned appointment's signature is invalid")
-        return False
-
-    logger.info("Appointment accepted and signed by Pisa")
-    # all good, store appointment and signature
-    try:
-        save_signed_appointment(appointment, signature)
-
-    except OSError as e:
-        logger.error("There was an error while saving the appointment", error=e)
-        return False
-
-    return True
-
 
 def get_appointment(args):
     if not args:
@@ -260,8 +275,9 @@ def get_appointment(args):
 
     try:
         r = requests.get(url=get_appointment_endpoint + parameters, timeout=5)
+        logger.info("Appointment response returned from server: " + str(r))
+        return True
 
-        print(json.dumps(r.json(), indent=4, sort_keys=True))
     except ConnectTimeout:
         logger.error("Can't connect to pisa API. Connection timeout")
         return False
@@ -270,7 +286,47 @@ def get_appointment(args):
         logger.error("Can't connect to pisa API. Server cannot be reached")
         return False
 
-    return True
+
+def get_appointment_signature(appointment):
+    try:
+        sk_der = load_key_file_data(CLI_PRIVATE_KEY)
+        cli_sk = Cryptographer.load_private_key_der(sk_der)
+
+        signature = Cryptographer.sign(appointment.serialize(), cli_sk)
+
+        return signature
+
+    except ValueError:
+        logger.error("Failed to deserialize the public key. It might be in an unsupported format")
+        return False
+
+    except FileNotFoundError:
+        logger.error("Client's private key file not found. Please check your settings")
+        return False
+
+    except IOError as e:
+        logger.error("I/O error", errno=e.errno, error=e.strerror)
+        return False
+
+
+def get_pk():
+    try:
+        cli_pk_der = load_key_file_data(CLI_PUBLIC_KEY)
+        hex_pk_der = binascii.hexlify(cli_pk_der)
+
+        return hex_pk_der
+
+    except FileNotFoundError:
+        logger.error("Client's public key file not found. Please check your settings")
+        return False
+
+    except IOError as e:
+        logger.error("I/O error", errno=e.errno, error=e.strerror)
+        return False
+
+    except binascii.Error as e:
+        logger.error("Could not successfully encode public key as hex: ", e)
+        return False
 
 
 def show_usage():
diff --git a/common/tools.py b/common/tools.py
index e527e33..2ac6d1e 100644
--- a/common/tools.py
+++ b/common/tools.py
@@ -1,4 +1,5 @@
 import re
+from common.constants import LOCATOR_LEN_HEX
 
 
 def check_sha256_hex_format(value):
@@ -12,3 +13,15 @@ def check_sha256_hex_format(value):
         :mod:`bool`: Whether or not the value matches the format.
     """
     return isinstance(value, str) and re.match(r"^[0-9A-Fa-f]{64}$", value) is not None
+
+
+def compute_locator(tx_id):
+    """
+    Computes an appointment locator given a transaction id.
+    Args:
+        tx_id (:obj:`str`): the transaction id used to compute the locator.
+    Returns:
+       (:obj:`str`): The computed locator.
+    """
+
+    return tx_id[:LOCATOR_LEN_HEX]
diff --git a/pisa/api.py b/pisa/api.py
index 519b3cb..a70ca34 100644
--- a/pisa/api.py
+++ b/pisa/api.py
@@ -17,21 +17,22 @@ logger = Logger("API")
 
 
 class API:
-    def __init__(self, watcher):
+    def __init__(self, watcher, config):
         self.watcher = watcher
+        self.config = config
 
     def add_appointment(self):
         """
         Main endpoint of the Watchtower.
 
-        The client sends requests (appointments) to this endpoint to request a job to the Watchtower. Requests must be json
-        encoded and contain an ``appointment`` field and optionally a ``signature`` and ``public_key`` fields.
+        The client sends requests (appointments) to this endpoint to request a job to the Watchtower. Requests must be
+        json encoded and contain an ``appointment`` field and optionally a ``signature`` and ``public_key`` fields.
 
         Returns:
-            :obj:`tuple`: A tuple containing the response (``json``) and response code (``int``). For accepted appointments,
-            the ``rcode`` is always 0 and the response contains the signed receipt. For rejected appointments, the ``rcode``
-            is a negative value and the response contains the error message. Error messages can be found at
-            :mod:`Errors <pisa.errors>`.
+            :obj:`tuple`: A tuple containing the response (``json``) and response code (``int``). For accepted
+            appointments, the ``rcode`` is always 0 and the response contains the signed receipt. For rejected
+            appointments, the ``rcode`` is a negative value and the response contains the error message. Error messages
+            can be found at :mod:`Errors <pisa.errors>`.
         """
 
         remote_addr = request.environ.get("REMOTE_ADDR")
@@ -41,7 +42,7 @@ class API:
 
         # Check content type once if properly defined
         request_data = json.loads(request.get_json())
-        inspector = Inspector()
+        inspector = Inspector(self.config)
         appointment = inspector.inspect(
             request_data.get("appointment"), request_data.get("signature"), request_data.get("public_key")
         )
@@ -165,8 +166,8 @@ class API:
         """
         Provides the block height of the Watchtower.
 
-        This is a testing endpoint that (most likely) will be removed in production. Its purpose is to give information to
-        testers about the current block so they can define a dummy appointment without having to run a bitcoin node.
+        This is a testing endpoint that (most likely) will be removed in production. Its purpose is to give information
+        to testers about the current block so they can define a dummy appointment without having to run a bitcoin node.
 
         Returns:
             :obj:`dict`: A json encoded dictionary containing the block height.
diff --git a/pisa/chain_monitor.py b/pisa/chain_monitor.py
new file mode 100644
index 0000000..689a223
--- /dev/null
+++ b/pisa/chain_monitor.py
@@ -0,0 +1,182 @@
+import zmq
+import binascii
+from threading import Thread, Event, Condition
+
+from common.logger import Logger
+from pisa.conf import FEED_PROTOCOL, FEED_ADDR, FEED_PORT, POLLING_DELTA, BLOCK_WINDOW_SIZE
+from pisa.block_processor import BlockProcessor
+
+logger = Logger("ChainMonitor")
+
+
+class ChainMonitor:
+    """
+    The :class:`ChainMonitor` is the class in charge of monitoring the blockchain (via ``bitcoind``) to detect new
+    blocks on top of the best chain. If a new best block is spotted, the chain monitor will notify the
+    :obj:`Watcher <pisa.watcher.Watcher>` and the :obj:`Responder <pisa.responder.Responder>` using ``Queues``.
+
+    The :class:`ChainMonitor` monitors the chain using two methods: ``zmq`` and ``polling``. Blocks are only notified
+    once per queue and the notification is triggered by the method that detects the block faster.
+
+    Attributes:
+        best_tip (:obj:`str`): a block hash representing the current best tip.
+        last_tips (:obj:`list`): a list of last chain tips. Used as a sliding window to avoid notifying about old tips.
+        terminate (:obj:`bool`): a flag to signal the termination of the :class:`ChainMonitor` (shutdown the tower).
+        check_tip (:obj:`Event`): an event that's triggered at fixed time intervals and controls the polling thread.
+        lock (:obj:`Condition`): a lock used to protect concurrent access to the queues and ``best_tip`` by the zmq and
+            polling threads.
+        zmqSubSocket (:obj:`socket`): a socket to connect to ``bitcoind`` via ``zmq``.
+        watcher_queue (:obj:`Queue`): a queue to send new best tips to the :obj:`Watcher <pisa.watcher.Watcher>`.
+        responder_queue (:obj:`Queue`): a queue to send new best tips to the
+            :obj:`Responder <pisa.responder.Responder>`.
+        watcher_asleep (:obj:`bool`): a flag that signals whether to send information to the ``Watcher`` or not.
+        responder_asleep (:obj:`bool`): a flag that signals whether to send information to the ``Responder`` or not.
+    """
+
+    def __init__(self):
+        self.best_tip = None
+        self.last_tips = []
+        self.terminate = False
+
+        self.check_tip = Event()
+        self.lock = Condition()
+
+        self.zmqContext = zmq.Context()
+        self.zmqSubSocket = self.zmqContext.socket(zmq.SUB)
+        self.zmqSubSocket.setsockopt(zmq.RCVHWM, 0)
+        self.zmqSubSocket.setsockopt_string(zmq.SUBSCRIBE, "hashblock")
+        self.zmqSubSocket.connect("%s://%s:%s" % (FEED_PROTOCOL, FEED_ADDR, FEED_PORT))
+
+        self.watcher_queue = None
+        self.responder_queue = None
+        self.watcher_asleep = True
+        self.responder_asleep = True
+
+    def attach_watcher(self, queue, asleep):
+        """
+        Attaches a :obj:`Watcher <pisa.watcher.Watcher>` to the :class:`ChainMonitor`. The ``Watcher`` and the
+        ``ChainMonitor`` are connected via the ``watcher_queue`` and the ``watcher_asleep`` flag.
+
+        Args:
+            queue (:obj:`Queue`): the queue to be used to send blocks hashes to the ``Watcher``.
+            asleep( :obj:`bool`): whether the ``Watcher`` is initially awake or asleep. It is changed on the fly from
+                the ``Watcher`` when the state changes.
+        """
+
+        self.watcher_queue = queue
+        self.watcher_asleep = asleep
+
+    def attach_responder(self, queue, asleep):
+        """
+        Attaches a :obj:`Responder <pisa.responder.Responder>` to the :class:`ChainMonitor`. The ``Responder`` and the
+        ``ChainMonitor`` are connected via the ``responder_queue`` and the ``responder_asleep`` flag.
+
+        Args:
+            queue (:obj:`Queue`): the queue to be used to send blocks hashes to the ``Responder``.
+            asleep( :obj:`bool`): whether the ``Responder`` is initially awake or asleep. It is changed on the fly from
+                the ``Responder`` when the state changes.
+        """
+
+        self.responder_queue = queue
+        self.responder_asleep = asleep
+
+    def notify_subscribers(self, block_hash):
+        """
+        Notifies the subscribers (``Watcher`` and ``Responder``) about a new block provided they are awake. It does so
+        by putting the hash in the corresponding queue(s).
+
+        Args:
+            block_hash (:obj:`str`): the new block hash to be sent to the awake subscribers.
+        """
+
+        if not self.watcher_asleep:
+            self.watcher_queue.put(block_hash)
+
+        if not self.responder_asleep:
+            self.responder_queue.put(block_hash)
+
+    def update_state(self, block_hash, max_block_window_size=BLOCK_WINDOW_SIZE):
+        """
+        Updates the state of the ``ChainMonitor``. The state is represented as the ``best_tip`` and the list of
+        ``last_tips``. ``last_tips`` is bounded to ``max_block_window_size``.
+
+        Args:
+            block_hash (:obj:`block_hash`): the new best tip.
+            max_block_window_size (:obj:`int`): the maximum length of the ``last_tips`` list.
+
+        Returns:
+            (:obj:`bool`): ``True`` is the state was successfully updated, ``False`` otherwise.
+        """
+
+        if block_hash != self.best_tip and block_hash not in self.last_tips:
+            self.last_tips.append(self.best_tip)
+            self.best_tip = block_hash
+
+            if len(self.last_tips) > max_block_window_size:
+                self.last_tips.pop(0)
+
+            return True
+
+        else:
+            return False
+
+    def monitor_chain_polling(self, polling_delta=POLLING_DELTA):
+        """
+        Monitors ``bitcoind`` via polling. Once the method is fired, it keeps monitoring as long as ``terminate`` is not
+        set. Polling is performed once every ``polling_delta`` seconds. If a new best tip if found, the shared lock is
+        acquired, the state is updated and the subscribers are notified, and finally the lock is released.
+
+        Args:
+             polling_delta (:obj:`int`): the time delta between polls.
+        """
+
+        while not self.terminate:
+            self.check_tip.wait(timeout=polling_delta)
+
+            # Terminate could have been set while the thread was blocked in wait
+            if not self.terminate:
+                current_tip = BlockProcessor.get_best_block_hash()
+
+                self.lock.acquire()
+                if self.update_state(current_tip):
+                    self.notify_subscribers(current_tip)
+                    logger.info("New block received via polling", block_hash=current_tip)
+                self.lock.release()
+
+    def monitor_chain_zmq(self):
+        """
+        Monitors ``bitcoind`` via zmq. Once the method is fired, it keeps monitoring as long as ``terminate`` is not
+        set. If a new best tip if found, the shared lock is acquired, the state is updated and the subscribers are
+        notified, and finally the lock is released.
+        """
+
+        while not self.terminate:
+            msg = self.zmqSubSocket.recv_multipart()
+
+            # Terminate could have been set while the thread was blocked in recv
+            if not self.terminate:
+                topic = msg[0]
+                body = msg[1]
+
+                if topic == b"hashblock":
+                    block_hash = binascii.hexlify(body).decode("utf-8")
+
+                    self.lock.acquire()
+                    if self.update_state(block_hash):
+                        self.notify_subscribers(block_hash)
+                        logger.info("New block received via zmq", block_hash=block_hash)
+                    self.lock.release()
+
+    def monitor_chain(self, polling_delta=POLLING_DELTA):
+        """
+        Main :class:`ChainMonitor` method. It initializes the ``best_tip`` to the current one (by querying the
+        :obj:`BlockProcessor <pisa.block_processor.BlockProcessor>`) and creates two threads, one per each monitoring
+        approach (``zmq`` and ``polling``).
+
+        Args:
+             polling_delta (:obj:`int`): the time delta between polls by the ``monitor_chain_polling`` thread.
+        """
+
+        self.best_tip = BlockProcessor.get_best_block_hash()
+        Thread(target=self.monitor_chain_polling, daemon=True, kwargs={"polling_delta": polling_delta}).start()
+        Thread(target=self.monitor_chain_zmq, daemon=True).start()
diff --git a/pisa/inspector.py b/pisa/inspector.py
index 00a7fc2..fcc570e 100644
--- a/pisa/inspector.py
+++ b/pisa/inspector.py
@@ -5,7 +5,6 @@ from common.constants import LOCATOR_LEN_HEX
 from common.cryptographer import Cryptographer
 
 from pisa import errors
-import pisa.conf as conf
 from common.logger import Logger
 from common.appointment import Appointment
 from pisa.block_processor import BlockProcessor
@@ -23,6 +22,9 @@ class Inspector:
     The :class:`Inspector` class is in charge of verifying that the appointment data provided by the user is correct.
     """
 
+    def __init__(self, config):
+        self.config = config
+
     def inspect(self, appointment_data, signature, public_key):
         """
         Inspects whether the data provided by the user is correct.
@@ -221,8 +223,7 @@ class Inspector:
 
         return rcode, message
 
-    @staticmethod
-    def check_to_self_delay(to_self_delay):
+    def check_to_self_delay(self, to_self_delay):
         """
         Checks if the provided ``to_self_delay`` is correct.
 
@@ -255,10 +256,10 @@ class Inspector:
             rcode = errors.APPOINTMENT_WRONG_FIELD_TYPE
             message = "wrong to_self_delay data type ({})".format(t)
 
-        elif to_self_delay < conf.MIN_TO_SELF_DELAY:
+        elif to_self_delay < self.config.get("MIN_TO_SELF_DELAY"):
             rcode = errors.APPOINTMENT_FIELD_TOO_SMALL
             message = "to_self_delay too small. The to_self_delay should be at least {} (current: {})".format(
-                conf.MIN_TO_SELF_DELAY, to_self_delay
+                self.config.get("MIN_TO_SELF_DELAY"), to_self_delay
             )
 
         if message is not None:
diff --git a/pisa/pisad.py b/pisa/pisad.py
index 9c258ce..6bc8b9c 100644
--- a/pisa/pisad.py
+++ b/pisa/pisad.py
@@ -2,14 +2,13 @@ from getopt import getopt
 from sys import argv, exit
 from signal import signal, SIGINT, SIGQUIT, SIGTERM
 
-from pisa.conf import DB_PATH
 from common.logger import Logger
 from pisa.api import API
 from pisa.watcher import Watcher
 from pisa.builder import Builder
-from pisa.conf import BTC_NETWORK, PISA_SECRET_KEY
-from pisa.responder import Responder
+import pisa.conf as conf
 from pisa.db_manager import DBManager
+from pisa.chain_monitor import ChainMonitor
 from pisa.block_processor import BlockProcessor
 from pisa.tools import can_connect_to_bitcoind, in_correct_network
 
@@ -19,11 +18,59 @@ logger = Logger("Daemon")
 def handle_signals(signal_received, frame):
     logger.info("Closing connection with appointments db")
     db_manager.db.close()
+    chain_monitor.terminate = True
 
     logger.info("Shutting down PISA")
     exit(0)
 
 
+def load_config(config):
+    """
+    Looks through all of the config options to make sure they contain the right type of data and builds a config
+    dictionary. 
+
+    Args:
+        config (:obj:`module`): It takes in a config module object.
+
+    Returns:
+        :obj:`dict` A dictionary containing the config values.
+    """
+
+    conf_dict = {}
+
+    conf_fields = {
+        "BTC_RPC_USER": {"value": config.BTC_RPC_USER, "type": str},
+        "BTC_RPC_PASSWD": {"value": config.BTC_RPC_PASSWD, "type": str},
+        "BTC_RPC_HOST": {"value": config.BTC_RPC_HOST, "type": str},
+        "BTC_RPC_PORT": {"value": config.BTC_RPC_PORT, "type": int},
+        "BTC_NETWORK": {"value": config.BTC_NETWORK, "type": str},
+        "FEED_PROTOCOL": {"value": config.FEED_PROTOCOL, "type": str},
+        "FEED_ADDR": {"value": config.FEED_ADDR, "type": str},
+        "FEED_PORT": {"value": config.FEED_PORT, "type": int},
+        "MAX_APPOINTMENTS": {"value": config.MAX_APPOINTMENTS, "type": int},
+        "EXPIRY_DELTA": {"value": config.EXPIRY_DELTA, "type": int},
+        "MIN_TO_SELF_DELAY": {"value": config.MIN_TO_SELF_DELAY, "type": int},
+        "SERVER_LOG_FILE": {"value": config.SERVER_LOG_FILE, "type": str},
+        "PISA_SECRET_KEY": {"value": config.PISA_SECRET_KEY, "type": str},
+        "CLIENT_LOG_FILE": {"value": config.CLIENT_LOG_FILE, "type": str},
+        "TEST_LOG_FILE": {"value": config.TEST_LOG_FILE, "type": str},
+        "DB_PATH": {"value": config.DB_PATH, "type": str},
+    }
+
+    for field in conf_fields:
+        value = conf_fields[field]["value"]
+        correct_type = conf_fields[field]["type"]
+
+        if (value is not None) and isinstance(value, correct_type):
+            conf_dict[field] = value
+        else:
+            err_msg = "{} variable in config is of the wrong type".format(field)
+            logger.error(err_msg)
+            raise ValueError(err_msg)
+
+    return conf_dict
+
+
 if __name__ == "__main__":
     logger.info("Starting PISA")
 
@@ -36,23 +83,31 @@ if __name__ == "__main__":
         # FIXME: Leaving this here for future option/arguments
         pass
 
+    pisa_config = load_config(conf)
+
     if not can_connect_to_bitcoind():
         logger.error("Can't connect to bitcoind. Shutting down")
 
-    elif not in_correct_network(BTC_NETWORK):
+    elif not in_correct_network(pisa_config.get("BTC_NETWORK")):
         logger.error("bitcoind is running on a different network, check conf.py and bitcoin.conf. Shutting down")
 
     else:
         try:
-            db_manager = DBManager(DB_PATH)
+            db_manager = DBManager(pisa_config.get("DB_PATH"))
+
+            # Create the chain monitor and start monitoring the chain
+            chain_monitor = ChainMonitor()
+            chain_monitor.monitor_chain()
 
             watcher_appointments_data = db_manager.load_watcher_appointments()
             responder_trackers_data = db_manager.load_responder_trackers()
 
-            with open(PISA_SECRET_KEY, "rb") as key_file:
+            with open(pisa_config.get("PISA_SECRET_KEY"), "rb") as key_file:
                 secret_key_der = key_file.read()
 
-            watcher = Watcher(db_manager, secret_key_der)
+            watcher = Watcher(db_manager, chain_monitor, secret_key_der, pisa_config)
+            chain_monitor.attach_watcher(watcher.block_queue, watcher.asleep)
+            chain_monitor.attach_responder(watcher.responder.block_queue, watcher.responder.asleep)
 
             if len(watcher_appointments_data) == 0 and len(responder_trackers_data) == 0:
                 logger.info("Fresh bootstrap")
@@ -65,7 +120,6 @@ if __name__ == "__main__":
                 last_block_responder = db_manager.load_last_block_hash_responder()
 
                 # FIXME: 32-reorgs-offline dropped txs are not used at this point.
-                responder = Responder(db_manager)
                 last_common_ancestor_responder = None
                 missed_blocks_responder = None
 
@@ -76,12 +130,12 @@ if __name__ == "__main__":
                     )
                     missed_blocks_responder = block_processor.get_missed_blocks(last_common_ancestor_responder)
 
-                    responder.trackers, responder.tx_tracker_map = Builder.build_trackers(responder_trackers_data)
-                    responder.block_queue = Builder.build_block_queue(missed_blocks_responder)
+                    watcher.responder.trackers, watcher.responder.tx_tracker_map = Builder.build_trackers(
+                        responder_trackers_data
+                    )
+                    watcher.responder.block_queue = Builder.build_block_queue(missed_blocks_responder)
 
-                # Build Watcher with Responder and backed up data. If the blocks of both match we don't perform the
-                # search twice.
-                watcher.responder = responder
+                # Build Watcher. If the blocks of both match we don't perform the search twice.
                 if last_block_watcher is not None:
                     if last_block_watcher == last_block_responder:
                         missed_blocks_watcher = missed_blocks_responder
@@ -97,7 +151,7 @@ if __name__ == "__main__":
                     watcher.block_queue = Builder.build_block_queue(missed_blocks_watcher)
 
             # Fire the API
-            API(watcher).start()
+            API(watcher, config=pisa_config).start()
 
         except Exception as e:
             logger.error("An error occurred: {}. Shutting down".format(e))
diff --git a/pisa/responder.py b/pisa/responder.py
index aa5f672..39f3777 100644
--- a/pisa/responder.py
+++ b/pisa/responder.py
@@ -6,7 +6,6 @@ from common.logger import Logger
 from pisa.cleaner import Cleaner
 from pisa.carrier import Carrier
 from pisa.block_processor import BlockProcessor
-from pisa.utils.zmq_subscriber import ZMQSubscriber
 
 CONFIRMATIONS_BEFORE_RETRY = 6
 MIN_CONFIRMATIONS = 6
@@ -128,22 +127,22 @@ class Responder:
             has missed. Used to trigger rebroadcast if needed.
         asleep (:obj:`bool`): A flag that signals whether the :obj:`Responder` is asleep or awake.
         block_queue (:obj:`Queue`): A queue used by the :obj:`Responder` to receive block hashes from ``bitcoind``. It
-            is populated by the :obj:`ZMQSubscriber <pisa.utils.zmq_subscriber.ZMQSubscriber>`.
-        zmq_subscriber (:obj:`ZMQSubscriber <pisa.utils.zmq_subscriber.ZMQSubscriber>`): a ``ZMQSubscriber`` instance
-            used to receive new block notifications from ``bitcoind``.
+            is populated by the :obj:`ChainMonitor <pisa.chain_monitor.ChainMonitor>`.
+        chain_monitor (:obj:`ChainMonitor <pisa.chain_monitor.ChainMonitor>`): a ``ChainMonitor`` instance used to track
+            new blocks received by ``bitcoind``.
         db_manager (:obj:`DBManager <pisa.db_manager.DBManager>`): A ``DBManager`` instance to interact with the
             database.
 
     """
 
-    def __init__(self, db_manager):
+    def __init__(self, db_manager, chain_monitor):
         self.trackers = dict()
         self.tx_tracker_map = dict()
         self.unconfirmed_txs = []
         self.missed_confirmations = dict()
         self.asleep = True
         self.block_queue = Queue()
-        self.zmq_subscriber = None
+        self.chain_monitor = chain_monitor
         self.db_manager = db_manager
 
     @staticmethod
@@ -226,8 +225,7 @@ class Responder:
         ``penalty_txid`` added to ``unconfirmed_txs`` if ``confirmations=0``. Finally, all the data is stored in the
         database.
 
-        ``add_tracker`` awakes the :obj:`Responder` and creates a connection with the
-        :obj:`ZMQSubscriber <pisa.utils.zmq_subscriber.ZMQSubscriber>` if he is asleep.
+        ``add_tracker`` awakes the :obj:`Responder` if it is asleep.
 
         Args:
             uuid (:obj:`str`): a unique identifier for the appointment.
@@ -268,19 +266,8 @@ class Responder:
 
         if self.asleep:
             self.asleep = False
-            zmq_thread = Thread(target=self.do_subscribe)
-            responder = Thread(target=self.do_watch)
-            zmq_thread.start()
-            responder.start()
-
-    def do_subscribe(self):
-        """
-        Initializes a :obj:`ZMQSubscriber <pisa.utils.zmq_subscriber.ZMQSubscriber>` instance to listen to new blocks
-        from ``bitcoind``. Block ids are received trough the ``block_queue``.
-        """
-
-        self.zmq_subscriber = ZMQSubscriber(parent="Responder")
-        self.zmq_subscriber.handle(self.block_queue)
+            self.chain_monitor.responder_asleep = False
+            Thread(target=self.do_watch).start()
 
     def do_watch(self):
         """
@@ -335,8 +322,7 @@ class Responder:
 
         # Go back to sleep if there are no more pending trackers
         self.asleep = True
-        self.zmq_subscriber.terminate = True
-        self.block_queue = Queue()
+        self.chain_monitor.responder_asleep = True
 
         logger.info("No more pending trackers, going back to sleep")
 
@@ -492,9 +478,6 @@ class Responder:
 
                 else:
                     # If the penalty transaction is missing, we need to reset the tracker.
-                    # DISCUSS: Adding tracker back, should we flag it as retried?
-                    # FIXME: Whether we decide to increase the retried counter or not, the current counter should be
-                    #        maintained. There is no way of doing so with the current approach. Update if required
                     self.handle_breach(
                         tracker.locator,
                         uuid,
diff --git a/pisa/sample_conf.py b/pisa/sample_conf.py
index 71e64a0..8d08590 100644
--- a/pisa/sample_conf.py
+++ b/pisa/sample_conf.py
@@ -5,6 +5,10 @@ BTC_RPC_HOST = "localhost"
 BTC_RPC_PORT = 18443
 BTC_NETWORK = "regtest"
 
+# CHAIN MONITOR
+POLLING_DELTA = 60
+BLOCK_WINDOW_SIZE = 10
+
 # ZMQ
 FEED_PROTOCOL = "tcp"
 FEED_ADDR = "127.0.0.1"
diff --git a/pisa/utils/zmq_subscriber.py b/pisa/utils/zmq_subscriber.py
index ecec9af..5bf29f5 100644
--- a/pisa/utils/zmq_subscriber.py
+++ b/pisa/utils/zmq_subscriber.py
@@ -8,12 +8,14 @@ from pisa.conf import FEED_PROTOCOL, FEED_ADDR, FEED_PORT
 class ZMQSubscriber:
     """ Adapted from https://github.com/bitcoin/bitcoin/blob/master/contrib/zmq/zmq_sub.py"""
 
-    def __init__(self, parent):
+    def __init__(self, config, parent):
         self.zmqContext = zmq.Context()
         self.zmqSubSocket = self.zmqContext.socket(zmq.SUB)
         self.zmqSubSocket.setsockopt(zmq.RCVHWM, 0)
         self.zmqSubSocket.setsockopt_string(zmq.SUBSCRIBE, "hashblock")
-        self.zmqSubSocket.connect("%s://%s:%s" % (FEED_PROTOCOL, FEED_ADDR, FEED_PORT))
+        self.zmqSubSocket.connect(
+            "%s://%s:%s" % (config.get("FEED_PROTOCOL"), config.get("FEED_ADDR"), config.get("FEED_PORT"))
+        )
         self.logger = Logger("ZMQSubscriber-{}".format(parent))
 
         self.terminate = False
diff --git a/pisa/watcher.py b/pisa/watcher.py
index 62ba514..828a45d 100644
--- a/pisa/watcher.py
+++ b/pisa/watcher.py
@@ -3,15 +3,14 @@ from queue import Queue
 from threading import Thread
 
 from common.cryptographer import Cryptographer
-from common.constants import LOCATOR_LEN_HEX
 from common.appointment import Appointment
+from common.tools import compute_locator
+
 from common.logger import Logger
 
 from pisa.cleaner import Cleaner
 from pisa.responder import Responder
 from pisa.block_processor import BlockProcessor
-from pisa.utils.zmq_subscriber import ZMQSubscriber
-from pisa.conf import EXPIRY_DELTA, MAX_APPOINTMENTS
 
 logger = Logger("Watcher")
 
@@ -29,15 +28,17 @@ class Watcher:
     If an appointment reaches its end with no breach, the data is simply deleted.
 
     The :class:`Watcher` receives information about new received blocks via the ``block_queue`` that is populated by the
-    :obj:`ZMQSubscriber <pisa.utils.zmq_subscriber>`.
+    :obj:`ChainMonitor <pisa.chain_monitor.ChainMonitor>`.
 
     Args:
         db_manager (:obj:`DBManager <pisa.db_manager>`): a ``DBManager`` instance to interact with the database.
+        chain_monitor (:obj:`ChainMonitor <pisa.chain_monitor.ChainMonitor>`): a ``ChainMonitor`` instance used to track
+            new blocks received by ``bitcoind``.
         sk_der (:obj:`bytes`): a DER encoded private key used to sign appointment receipts (signaling acceptance).
+        config (:obj:`dict`): a dictionary containing all the configuration parameters. Used locally to retrieve
+            ``MAX_APPOINTMENTS``  and ``EXPIRY_DELTA``.
         responder (:obj:`Responder <pisa.responder.Responder>`): a ``Responder`` instance. If ``None`` is passed, a new
             instance is created. Populated instances are useful when bootstrapping the system from backed-up data.
-        max_appointments(:obj:`int`): the maximum amount of appointments that the :obj:`Watcher` will keep at any given
-            time. Defaults to ``MAX_APPOINTMENTS``.
 
 
     Attributes:
@@ -48,44 +49,31 @@ class Watcher:
             appointments with the same ``locator``.
         asleep (:obj:`bool`): A flag that signals whether the :obj:`Watcher` is asleep or awake.
         block_queue (:obj:`Queue`): A queue used by the :obj:`Watcher` to receive block hashes from ``bitcoind``. It is
-            populated by the :obj:`ZMQSubscriber <pisa.utils.zmq_subscriber.ZMQSubscriber>`.
-        max_appointments(:obj:`int`): the maximum amount of appointments that the :obj:`Watcher` will keep at any given
-            time.
-        zmq_subscriber (:obj:`ZMQSubscriber <pisa.utils.zmq_subscriber.ZMQSubscriber>`): a ZMQSubscriber instance used
-            to receive new block notifications from ``bitcoind``.
+        populated by the :obj:`ChainMonitor <pisa.chain_monitor.ChainMonitor>`.
+        chain_monitor (:obj:`ChainMonitor <pisa.chain_monitor.ChainMonitor>`): a ``ChainMonitor`` instance used to track
+            new blocks received by ``bitcoind``.
+        config (:obj:`dict`): a dictionary containing all the configuration parameters. Used locally to retrieve
+            ``MAX_APPOINTMENTS``  and ``EXPIRY_DELTA``.
         db_manager (:obj:`DBManager <pisa.db_manager>`): A db manager instance to interact with the database.
+        signing_key (:mod:`EllipticCurvePrivateKey`): a private key used to sign accepted appointments.
 
     Raises:
         ValueError: if `pisa_sk_file` is not found.
 
     """
 
-    def __init__(self, db_manager, sk_der, responder=None, max_appointments=MAX_APPOINTMENTS):
+    def __init__(self, db_manager, chain_monitor, sk_der, config, responder=None):
         self.appointments = dict()
         self.locator_uuid_map = dict()
         self.asleep = True
         self.block_queue = Queue()
-        self.max_appointments = max_appointments
-        self.zmq_subscriber = None
+        self.chain_monitor = chain_monitor
+        self.config = config
         self.db_manager = db_manager
         self.signing_key = Cryptographer.load_private_key_der(sk_der)
 
         if not isinstance(responder, Responder):
-            self.responder = Responder(db_manager)
-
-    @staticmethod
-    def compute_locator(tx_id):
-        """
-        Computes an appointment locator given a transaction id.
-
-        Args:
-            tx_id (:obj:`str`): the transaction id used to compute the locator.
-
-        Returns:
-           (:obj:`str`): The computed locator.
-        """
-
-        return tx_id[:LOCATOR_LEN_HEX]
+            self.responder = Responder(db_manager, chain_monitor)
 
     def add_appointment(self, appointment):
         """
@@ -117,8 +105,8 @@ class Watcher:
 
         """
 
-        if len(self.appointments) < self.max_appointments:
-            # Appointments are stored in disk, we only keep the end_time, locator and locator_uuid map in memory
+        if len(self.appointments) < self.config.get("MAX_APPOINTMENTS"):
+
             uuid = uuid4().hex
             self.appointments[uuid] = {"locator": appointment.locator, "end_time": appointment.end_time}
 
@@ -130,10 +118,8 @@ class Watcher:
 
             if self.asleep:
                 self.asleep = False
-                zmq_thread = Thread(target=self.do_subscribe)
-                watcher = Thread(target=self.do_watch)
-                zmq_thread.start()
-                watcher.start()
+                self.chain_monitor.watcher_asleep = False
+                Thread(target=self.do_watch).start()
 
                 logger.info("Waking up")
 
@@ -153,15 +139,6 @@ class Watcher:
 
         return appointment_added, signature
 
-    def do_subscribe(self):
-        """
-        Initializes a ``ZMQSubscriber`` instance to listen to new blocks from ``bitcoind``. Block ids are received
-        trough the ``block_queue``.
-        """
-
-        self.zmq_subscriber = ZMQSubscriber(parent="Watcher")
-        self.zmq_subscriber.handle(self.block_queue)
-
     def do_watch(self):
         """
         Monitors the blockchain whilst there are pending appointments.
@@ -184,7 +161,7 @@ class Watcher:
                 expired_appointments = [
                     uuid
                     for uuid, appointment_data in self.appointments.items()
-                    if block["height"] > appointment_data.get("end_time") + EXPIRY_DELTA
+                    if block["height"] > appointment_data.get("end_time") + self.config.get("EXPIRY_DELTA")
                 ]
 
                 Cleaner.delete_expired_appointment(
@@ -223,8 +200,7 @@ class Watcher:
 
         # Go back to sleep if there are no more appointments
         self.asleep = True
-        self.zmq_subscriber.terminate = True
-        self.block_queue = Queue()
+        self.chain_monitor.watcher_asleep = True
 
         logger.info("No more pending appointments, going back to sleep")
 
@@ -240,7 +216,7 @@ class Watcher:
             found.
         """
 
-        potential_locators = {Watcher.compute_locator(txid): txid for txid in txids}
+        potential_locators = {compute_locator(txid): txid for txid in txids}
 
         # Check is any of the tx_ids in the received block is an actual match
         intersection = set(self.locator_uuid_map.keys()).intersection(potential_locators.keys())
diff --git a/test/apps/cli/unit/test_pisa_cli.py b/test/apps/cli/unit/test_pisa_cli.py
index e14fd0b..74c6a95 100644
--- a/test/apps/cli/unit/test_pisa_cli.py
+++ b/test/apps/cli/unit/test_pisa_cli.py
@@ -1,23 +1,41 @@
 import responses
 import json
+import os
+import shutil
 from binascii import hexlify
 
 from cryptography.hazmat.backends import default_backend
-from cryptography.hazmat.primitives import hashes
+from cryptography.hazmat.primitives import serialization
 from cryptography.hazmat.primitives.asymmetric import ec
 
+from common.appointment import Appointment
+from common.cryptographer import Cryptographer
+
 import apps.cli.pisa_cli as pisa_cli
 from test.apps.cli.unit.conftest import get_random_value_hex
 
-# TODO: should find a way of doing without this
-from apps.cli.pisa_cli import build_appointment
-
 # dummy keys for the tests
 pisa_sk = ec.generate_private_key(ec.SECP256K1, default_backend())
 pisa_pk = pisa_sk.public_key()
 
 other_sk = ec.generate_private_key(ec.SECP256K1, default_backend())
 
+pisa_sk_der = pisa_sk.private_bytes(
+    encoding=serialization.Encoding.DER,
+    format=serialization.PrivateFormat.TraditionalOpenSSL,
+    encryption_algorithm=serialization.NoEncryption(),
+)
+pisa_pk_der = pisa_pk.public_bytes(
+    encoding=serialization.Encoding.DER, format=serialization.PublicFormat.SubjectPublicKeyInfo
+)
+
+other_sk_der = other_sk.private_bytes(
+    encoding=serialization.Encoding.DER,
+    format=serialization.PrivateFormat.TraditionalOpenSSL,
+    encryption_algorithm=serialization.NoEncryption(),
+)
+
+
 # Replace the key in the module with a key we control for the tests
 pisa_cli.pisa_public_key = pisa_pk
 # Replace endpoint with dummy one
@@ -32,18 +50,47 @@ dummy_appointment_request = {
     "end_time": 50000,
     "to_self_delay": 200,
 }
-dummy_appointment = build_appointment(**dummy_appointment_request)
 
-# FIXME: USE CRYPTOGRAPHER
+# This is the format appointment turns into once it hits "add_appointment"
+dummy_appointment_full = {
+    "locator": get_random_value_hex(32),
+    "start_time": 1500,
+    "end_time": 50000,
+    "to_self_delay": 200,
+    "encrypted_blob": get_random_value_hex(120),
+}
+
+dummy_appointment = Appointment.from_dict(dummy_appointment_full)
 
 
-def sign_appointment(sk, appointment):
-    data = json.dumps(appointment, sort_keys=True, separators=(",", ":")).encode("utf-8")
-    return hexlify(sk.sign(data, ec.ECDSA(hashes.SHA256()))).decode("utf-8")
+def get_dummy_pisa_sk_der(*args):
+    return pisa_sk_der
 
 
-def get_dummy_pisa_pk(der_data):
-    return pisa_pk
+def get_dummy_pisa_pk_der(*args):
+    return pisa_pk_der
+
+
+def get_dummy_hex_pk_der(*args):
+    return hexlify(get_dummy_pisa_pk_der())
+
+
+def get_dummy_signature(*args):
+    sk = Cryptographer.load_private_key_der(pisa_sk_der)
+    return Cryptographer.sign(dummy_appointment.serialize(), sk)
+
+
+def get_bad_signature(*args):
+    sk = Cryptographer.load_private_key_der(other_sk_der)
+    return Cryptographer.sign(dummy_appointment.serialize(), sk)
+
+
+def valid_sig(*args):
+    return True
+
+
+def invalid_sig(*args):
+    return False
 
 
 @responses.activate
@@ -51,10 +98,12 @@ def test_add_appointment(monkeypatch):
     # Simulate a request to add_appointment for dummy_appointment, make sure that the right endpoint is requested
     # and the return value is True
 
-    # make sure the test uses the right dummy key instead of loading it from disk
-    monkeypatch.setattr(pisa_cli, "load_public_key", get_dummy_pisa_pk)
+    # Make sure the test uses the dummy signature
+    monkeypatch.setattr(pisa_cli, "get_appointment_signature", get_dummy_signature)
+    monkeypatch.setattr(pisa_cli, "get_pk", get_dummy_hex_pk_der)
+    monkeypatch.setattr(pisa_cli, "check_signature", valid_sig)
 
-    response = {"locator": dummy_appointment["locator"], "signature": sign_appointment(pisa_sk, dummy_appointment)}
+    response = {"locator": dummy_appointment.to_dict()["locator"], "signature": get_dummy_signature()}
 
     request_url = "http://{}/".format(pisa_endpoint)
     responses.add(responses.POST, request_url, json=response, status=200)
@@ -72,12 +121,14 @@ def test_add_appointment_with_invalid_signature(monkeypatch):
     # Simulate a request to add_appointment for dummy_appointment, but sign with a different key,
     # make sure that the right endpoint is requested, but the return value is False
 
-    # make sure the test uses the right dummy key instead of loading it from disk
-    monkeypatch.setattr(pisa_cli, "load_public_key", get_dummy_pisa_pk)
+    # Make sure the test uses the bad dummy signature
+    monkeypatch.setattr(pisa_cli, "get_appointment_signature", get_bad_signature)
+    monkeypatch.setattr(pisa_cli, "get_pk", get_dummy_hex_pk_der)
+    monkeypatch.setattr(pisa_cli, "check_signature", invalid_sig)
 
     response = {
-        "locator": dummy_appointment["locator"],
-        "signature": sign_appointment(other_sk, dummy_appointment),  # signing with a different key
+        "locator": dummy_appointment.to_dict()["locator"],
+        "signature": get_bad_signature(),  # Sign with a bad key
     }
 
     request_url = "http://{}/".format(pisa_endpoint)
@@ -85,4 +136,141 @@ def test_add_appointment_with_invalid_signature(monkeypatch):
 
     result = pisa_cli.add_appointment([json.dumps(dummy_appointment_request)])
 
-    assert not result
+    assert result is False
+
+
+def test_load_key_file_data():
+    # If file exists and has data in it, function should work.
+    with open("key_test_file", "w+b") as f:
+        f.write(pisa_sk_der)
+
+    appt_data = pisa_cli.load_key_file_data("key_test_file")
+    assert appt_data
+
+    os.remove("key_test_file")
+
+    # If file doesn't exist, function should fail.
+    appt_data = pisa_cli.load_key_file_data("nonexistent_file")
+    assert not appt_data
+
+
+def test_save_signed_appointment(monkeypatch):
+    monkeypatch.setattr(pisa_cli, "APPOINTMENTS_FOLDER_NAME", "test_appointments")
+
+    pisa_cli.save_signed_appointment(dummy_appointment.to_dict(), get_dummy_signature())
+
+    # In folder "Appointments," grab all files and print them.
+    files = os.listdir("test_appointments")
+
+    found = False
+    for f in files:
+        if dummy_appointment.to_dict().get("locator") in f:
+            found = True
+
+    assert found
+
+    # If "appointments" directory doesn't exist, function should create it.
+    assert os.path.exists("test_appointments")
+
+    # Delete test directory once we're done.
+    shutil.rmtree("test_appointments")
+
+
+def test_parse_add_appointment_args():
+    # If no args are passed, function should fail.
+    appt_data = pisa_cli.parse_add_appointment_args(None)
+    assert not appt_data
+
+    # If file doesn't exist, function should fail.
+    appt_data = pisa_cli.parse_add_appointment_args(["-f", "nonexistent_file"])
+    assert not appt_data
+
+    # If file exists and has data in it, function should work.
+    with open("appt_test_file", "w") as f:
+        json.dump(dummy_appointment_request, f)
+
+    appt_data = pisa_cli.parse_add_appointment_args(["-f", "appt_test_file"])
+    assert appt_data
+
+    os.remove("appt_test_file")
+
+    # If appointment json is passed in, function should work.
+    appt_data = pisa_cli.parse_add_appointment_args([json.dumps(dummy_appointment_request)])
+    assert appt_data
+
+
+@responses.activate
+def test_post_data_to_add_appointment_endpoint():
+    response = {
+        "locator": dummy_appointment.to_dict()["locator"],
+        "signature": Cryptographer.sign(dummy_appointment.serialize(), pisa_sk),
+    }
+
+    request_url = "http://{}/".format(pisa_endpoint)
+    responses.add(responses.POST, request_url, json=response, status=200)
+
+    response = pisa_cli.post_data_to_add_appointment_endpoint(request_url, json.dumps(dummy_appointment_request))
+
+    assert len(responses.calls) == 1
+    assert responses.calls[0].request.url == request_url
+
+    assert response
+
+
+def test_check_signature(monkeypatch):
+    # Make sure the test uses the right dummy key instead of loading it from disk
+    monkeypatch.setattr(pisa_cli, "load_key_file_data", get_dummy_pisa_pk_der)
+
+    valid = pisa_cli.check_signature(get_dummy_signature(), dummy_appointment)
+
+    assert valid
+
+    valid = pisa_cli.check_signature(get_bad_signature(), dummy_appointment)
+
+    assert not valid
+
+
+@responses.activate
+def test_get_appointment():
+    # Response of get_appointment endpoint is an appointment with status added to it.
+    dummy_appointment_full["status"] = "being_watched"
+    response = dummy_appointment_full
+
+    request_url = "http://{}/".format(pisa_endpoint) + "get_appointment?locator={}".format(response.get("locator"))
+    responses.add(responses.GET, request_url, json=response, status=200)
+
+    result = pisa_cli.get_appointment([response.get("locator")])
+
+    assert len(responses.calls) == 1
+    assert responses.calls[0].request.url == request_url
+
+    assert result
+
+
+@responses.activate
+def test_get_appointment_err():
+    locator = get_random_value_hex(32)
+
+    # Test that get_appointment handles a connection error appropriately.
+    request_url = "http://{}/".format(pisa_endpoint) + "get_appointment?locator=".format(locator)
+    responses.add(responses.GET, request_url, body=ConnectionError())
+
+    assert not pisa_cli.get_appointment([locator])
+
+
+def test_get_appointment_signature(monkeypatch):
+    # Make sure the test uses the right dummy key instead of loading it from disk
+    monkeypatch.setattr(pisa_cli, "load_key_file_data", get_dummy_pisa_sk_der)
+
+    signature = pisa_cli.get_appointment_signature(dummy_appointment)
+
+    assert isinstance(signature, str)
+
+
+def test_get_pk(monkeypatch):
+    # Make sure the test uses the right dummy key instead of loading it from disk
+    monkeypatch.setattr(pisa_cli, "load_key_file_data", get_dummy_pisa_pk_der)
+
+    pk = pisa_cli.get_pk()
+
+    assert isinstance(pk, bytes)
diff --git a/test/pisa/unit/conftest.py b/test/pisa/unit/conftest.py
index 4ff9028..ff79fee 100644
--- a/test/pisa/unit/conftest.py
+++ b/test/pisa/unit/conftest.py
@@ -12,10 +12,11 @@ from cryptography.hazmat.primitives import serialization
 
 from apps.cli.blob import Blob
 from pisa.responder import TransactionTracker
-from pisa.watcher import Watcher
 from pisa.tools import bitcoin_cli
 from pisa.db_manager import DBManager
+from pisa.chain_monitor import ChainMonitor
 from common.appointment import Appointment
+from common.tools import compute_locator
 
 from bitcoind_mock.utils import sha256d
 from bitcoind_mock.transaction import TX
@@ -50,6 +51,17 @@ def db_manager():
     rmtree("test_db")
 
 
+@pytest.fixture(scope="module")
+def chain_monitor():
+    chain_monitor = ChainMonitor()
+    chain_monitor.monitor_chain()
+
+    yield chain_monitor
+
+    chain_monitor.terminate = True
+    generate_block()
+
+
 def generate_keypair():
     client_sk = ec.generate_private_key(ec.SECP256K1, default_backend())
     client_pk = client_sk.public_key()
@@ -103,7 +115,7 @@ def generate_dummy_appointment_data(real_height=True, start_time_offset=5, end_t
         encoding=serialization.Encoding.DER, format=serialization.PublicFormat.SubjectPublicKeyInfo
     )
 
-    locator = Watcher.compute_locator(dispute_txid)
+    locator = compute_locator(dispute_txid)
     blob = Blob(dummy_appointment_data.get("tx"))
 
     encrypted_blob = Cryptographer.encrypt(blob, dummy_appointment_data.get("tx_id"))
@@ -147,3 +159,26 @@ def generate_dummy_tracker():
     )
 
     return TransactionTracker.from_dict(tracker_data)
+
+
+def get_config():
+    config = {
+        "BTC_RPC_USER": "username",
+        "BTC_RPC_PASSWD": "password",
+        "BTC_RPC_HOST": "localhost",
+        "BTC_RPC_PORT": 8332,
+        "BTC_NETWORK": "regtest",
+        "FEED_PROTOCOL": "tcp",
+        "FEED_ADDR": "127.0.0.1",
+        "FEED_PORT": 28332,
+        "MAX_APPOINTMENTS": 100,
+        "EXPIRY_DELTA": 6,
+        "MIN_TO_SELF_DELAY": 20,
+        "SERVER_LOG_FILE": "pisa.log",
+        "PISA_SECRET_KEY": "pisa_sk.der",
+        "CLIENT_LOG_FILE": "pisa.log",
+        "TEST_LOG_FILE": "test.log",
+        "DB_PATH": "appointments",
+    }
+
+    return config
diff --git a/test/pisa/unit/test_api.py b/test/pisa/unit/test_api.py
index 2dc830b..f94ab40 100644
--- a/test/pisa/unit/test_api.py
+++ b/test/pisa/unit/test_api.py
@@ -9,7 +9,6 @@ from pisa.api import API
 from pisa.watcher import Watcher
 from pisa.tools import bitcoin_cli
 from pisa import HOST, PORT
-from pisa.conf import MAX_APPOINTMENTS
 
 from test.pisa.unit.conftest import (
     generate_block,
@@ -17,6 +16,7 @@ from test.pisa.unit.conftest import (
     get_random_value_hex,
     generate_dummy_appointment_data,
     generate_keypair,
+    get_config,
 )
 
 from common.constants import LOCATOR_LEN_BYTES
@@ -28,18 +28,23 @@ MULTIPLE_APPOINTMENTS = 10
 appointments = []
 locator_dispute_tx_map = {}
 
+config = get_config()
+
 
 @pytest.fixture(scope="module")
-def run_api(db_manager):
+def run_api(db_manager, chain_monitor):
     sk, pk = generate_keypair()
     sk_der = sk.private_bytes(
         encoding=serialization.Encoding.DER,
         format=serialization.PrivateFormat.TraditionalOpenSSL,
         encryption_algorithm=serialization.NoEncryption(),
     )
-    watcher = Watcher(db_manager, sk_der)
 
-    api_thread = Thread(target=API(watcher).start)
+    watcher = Watcher(db_manager, chain_monitor, sk_der, get_config())
+    chain_monitor.attach_watcher(watcher.block_queue, watcher.asleep)
+    chain_monitor.attach_responder(watcher.responder.block_queue, watcher.responder.asleep)
+
+    api_thread = Thread(target=API(watcher, config).start)
     api_thread.daemon = True
     api_thread.start()
 
@@ -102,7 +107,7 @@ def test_request_multiple_appointments_same_locator(new_appt_data, n=MULTIPLE_AP
 
 
 def test_add_too_many_appointment(new_appt_data):
-    for _ in range(MAX_APPOINTMENTS - len(appointments)):
+    for _ in range(config.get("MAX_APPOINTMENTS") - len(appointments)):
         r = add_appointment(new_appt_data)
         assert r.status_code == 200
 
diff --git a/test/pisa/unit/test_chain_monitor.py b/test/pisa/unit/test_chain_monitor.py
new file mode 100644
index 0000000..3c2bee6
--- /dev/null
+++ b/test/pisa/unit/test_chain_monitor.py
@@ -0,0 +1,225 @@
+import zmq
+import time
+from threading import Thread, Event, Condition
+
+from pisa.watcher import Watcher
+from pisa.responder import Responder
+from pisa.block_processor import BlockProcessor
+from pisa.chain_monitor import ChainMonitor
+
+from test.pisa.unit.conftest import get_random_value_hex, generate_block, get_config
+
+
+def test_init(run_bitcoind):
+    # run_bitcoind is started here instead of later on to avoid race conditions while it initializes
+
+    # Not much to test here, just sanity checks to make sure nothing goes south in the future
+    chain_monitor = ChainMonitor()
+
+    assert chain_monitor.best_tip is None
+    assert isinstance(chain_monitor.last_tips, list) and len(chain_monitor.last_tips) == 0
+    assert chain_monitor.terminate is False
+    assert isinstance(chain_monitor.check_tip, Event)
+    assert isinstance(chain_monitor.lock, Condition)
+    assert isinstance(chain_monitor.zmqSubSocket, zmq.Socket)
+
+    # The Queues and asleep flags are initialized when attaching the corresponding subscriber
+    assert chain_monitor.watcher_queue is None
+    assert chain_monitor.responder_queue is None
+    assert chain_monitor.watcher_asleep and chain_monitor.responder_asleep
+
+
+def test_attach_watcher(chain_monitor):
+    watcher = Watcher(db_manager=None, chain_monitor=chain_monitor, sk_der=None, config=get_config())
+    chain_monitor.attach_watcher(watcher.block_queue, watcher.asleep)
+
+    # booleans are not passed as reference in Python, so the flags need to be set separately
+    assert watcher.asleep == chain_monitor.watcher_asleep
+    watcher.asleep = False
+    assert chain_monitor.watcher_asleep != watcher.asleep
+
+    # Test that the Queue work
+    r_hash = get_random_value_hex(32)
+    chain_monitor.watcher_queue.put(r_hash)
+    assert watcher.block_queue.get() == r_hash
+
+
+def test_attach_responder(chain_monitor):
+    responder = Responder(db_manager=None, chain_monitor=chain_monitor)
+    chain_monitor.attach_responder(responder.block_queue, responder.asleep)
+
+    # Same kind of testing as with the attach watcher
+    assert responder.asleep == chain_monitor.watcher_asleep
+    responder.asleep = False
+    assert chain_monitor.watcher_asleep != responder.asleep
+
+    r_hash = get_random_value_hex(32)
+    chain_monitor.responder_queue.put(r_hash)
+    assert responder.block_queue.get() == r_hash
+
+
+def test_notify_subscribers(chain_monitor):
+    # Subscribers are only notified as long as they are awake
+    new_block = get_random_value_hex(32)
+
+    # Queues should be empty to start with
+    assert chain_monitor.watcher_queue.empty()
+    assert chain_monitor.responder_queue.empty()
+
+    chain_monitor.watcher_asleep = True
+    chain_monitor.responder_asleep = True
+    chain_monitor.notify_subscribers(new_block)
+
+    # And remain empty afterwards since both subscribers were asleep
+    assert chain_monitor.watcher_queue.empty()
+    assert chain_monitor.responder_queue.empty()
+
+    # Let's flag them as awake and try again
+    chain_monitor.watcher_asleep = False
+    chain_monitor.responder_asleep = False
+    chain_monitor.notify_subscribers(new_block)
+
+    assert chain_monitor.watcher_queue.get() == new_block
+    assert chain_monitor.responder_queue.get() == new_block
+
+
+def test_update_state(chain_monitor):
+    # The state is updated after receiving a new block (and only if the block is not already known).
+    # Let's start by setting a best_tip and a couple of old tips
+    new_block_hash = get_random_value_hex(32)
+    chain_monitor.best_tip = new_block_hash
+    chain_monitor.last_tips = [get_random_value_hex(32) for _ in range(5)]
+
+    # Now we can try to update the state with an old best_tip and see how it doesn't work
+    assert chain_monitor.update_state(chain_monitor.last_tips[0]) is False
+
+    # Same should happen with the current tip
+    assert chain_monitor.update_state(chain_monitor.best_tip) is False
+
+    # The state should be correctly updated with a new block hash, the chain tip should change and the old tip should
+    # have been added to the last_tips
+    another_block_hash = get_random_value_hex(32)
+    assert chain_monitor.update_state(another_block_hash) is True
+    assert chain_monitor.best_tip == another_block_hash and new_block_hash == chain_monitor.last_tips[-1]
+
+
+def test_monitor_chain_polling():
+    # Try polling with the Watcher
+    chain_monitor = ChainMonitor()
+    chain_monitor.best_tip = BlockProcessor.get_best_block_hash()
+
+    watcher = Watcher(db_manager=None, chain_monitor=chain_monitor, sk_der=None, config=get_config())
+    chain_monitor.attach_watcher(watcher.block_queue, asleep=False)
+
+    # monitor_chain_polling runs until terminate if set
+    polling_thread = Thread(target=chain_monitor.monitor_chain_polling, kwargs={"polling_delta": 0.1}, daemon=True)
+    polling_thread.start()
+
+    # Check that nothing changes as long as a block is not generated
+    for _ in range(5):
+        assert chain_monitor.watcher_queue.empty()
+        time.sleep(0.1)
+
+    # And that it does if we generate a block
+    generate_block()
+
+    chain_monitor.watcher_queue.get()
+    assert chain_monitor.watcher_queue.empty()
+
+    chain_monitor.terminate = True
+    polling_thread.join()
+
+
+def test_monitor_chain_zmq():
+    # Try zmq with the Responder
+    chain_monitor = ChainMonitor()
+    chain_monitor.best_tip = BlockProcessor.get_best_block_hash()
+
+    responder = Responder(db_manager=None, chain_monitor=chain_monitor)
+    chain_monitor.attach_responder(responder.block_queue, asleep=False)
+
+    zmq_thread = Thread(target=chain_monitor.monitor_chain_zmq, daemon=True)
+    zmq_thread.start()
+
+    # Queues should start empty
+    assert chain_monitor.responder_queue.empty()
+
+    # And have a new block every time we generate one
+    for _ in range(3):
+        generate_block()
+        chain_monitor.responder_queue.get()
+        assert chain_monitor.responder_queue.empty()
+
+    # If we flag it to sleep no notification is sent
+    chain_monitor.responder_asleep = True
+
+    for _ in range(3):
+        generate_block()
+        assert chain_monitor.responder_queue.empty()
+
+    chain_monitor.terminate = True
+    # The zmq thread needs a block generation to release from the recv method.
+    generate_block()
+
+    zmq_thread.join()
+
+
+def test_monitor_chain():
+    # Not much to test here, this should launch two threads (one per monitor approach) and finish on terminate
+    chain_monitor = ChainMonitor()
+
+    watcher = Watcher(db_manager=None, chain_monitor=chain_monitor, sk_der=None, config=get_config())
+    responder = Responder(db_manager=None, chain_monitor=chain_monitor)
+    chain_monitor.attach_responder(responder.block_queue, asleep=False)
+    chain_monitor.attach_watcher(watcher.block_queue, asleep=False)
+
+    chain_monitor.best_tip = None
+    chain_monitor.monitor_chain()
+
+    # The tip is updated before starting the threads, so it should have changed.
+    assert chain_monitor.best_tip is not None
+
+    # Blocks should be received
+    for _ in range(5):
+        generate_block()
+        watcher_block = chain_monitor.watcher_queue.get()
+        responder_block = chain_monitor.responder_queue.get()
+        assert watcher_block == responder_block
+        assert chain_monitor.watcher_queue.empty()
+        assert chain_monitor.responder_queue.empty()
+
+    # And the thread be terminated on terminate
+    chain_monitor.terminate = True
+    # The zmq thread needs a block generation to release from the recv method.
+    generate_block()
+
+
+def test_monitor_chain_single_update():
+    # This test tests that if both threads try to add the same block to the queue, only the first one will make it
+    chain_monitor = ChainMonitor()
+
+    watcher = Watcher(db_manager=None, chain_monitor=chain_monitor, sk_der=None, config=get_config())
+    responder = Responder(db_manager=None, chain_monitor=chain_monitor)
+    chain_monitor.attach_responder(responder.block_queue, asleep=False)
+    chain_monitor.attach_watcher(watcher.block_queue, asleep=False)
+
+    chain_monitor.best_tip = None
+
+    # We will create a block and wait for the polling thread. Then check the queues to see that the block hash has only
+    # been added once.
+    chain_monitor.monitor_chain(polling_delta=2)
+    generate_block()
+
+    watcher_block = chain_monitor.watcher_queue.get()
+    responder_block = chain_monitor.responder_queue.get()
+    assert watcher_block == responder_block
+    assert chain_monitor.watcher_queue.empty()
+    assert chain_monitor.responder_queue.empty()
+
+    # The delta for polling is 2 secs, so let's wait and see
+    time.sleep(2)
+    assert chain_monitor.watcher_queue.empty()
+    assert chain_monitor.responder_queue.empty()
+
+    # We can also force an update and see that it won't go through
+    assert chain_monitor.update_state(watcher_block) is False
diff --git a/test/pisa/unit/test_inspector.py b/test/pisa/unit/test_inspector.py
index 7b18460..4dbafce 100644
--- a/test/pisa/unit/test_inspector.py
+++ b/test/pisa/unit/test_inspector.py
@@ -10,13 +10,13 @@ from common.appointment import Appointment
 from pisa.block_processor import BlockProcessor
 from pisa.conf import MIN_TO_SELF_DELAY
 
-from test.pisa.unit.conftest import get_random_value_hex, generate_dummy_appointment_data, generate_keypair
+from test.pisa.unit.conftest import get_random_value_hex, generate_dummy_appointment_data, generate_keypair, get_config
 
 from common.constants import LOCATOR_LEN_BYTES, LOCATOR_LEN_HEX
 from common.cryptographer import Cryptographer
 
 
-inspector = Inspector()
+inspector = Inspector(get_config())
 APPOINTMENT_OK = (0, None)
 
 NO_HEX_STRINGS = [
@@ -126,21 +126,21 @@ def test_check_to_self_delay():
     # Right value, right format
     to_self_delays = [MIN_TO_SELF_DELAY, MIN_TO_SELF_DELAY + 1, MIN_TO_SELF_DELAY + 1000]
     for to_self_delay in to_self_delays:
-        assert Inspector.check_to_self_delay(to_self_delay) == APPOINTMENT_OK
+        assert inspector.check_to_self_delay(to_self_delay) == APPOINTMENT_OK
 
     # to_self_delay too small
     to_self_delays = [MIN_TO_SELF_DELAY - 1, MIN_TO_SELF_DELAY - 2, 0, -1, -1000]
     for to_self_delay in to_self_delays:
-        assert Inspector.check_to_self_delay(to_self_delay)[0] == APPOINTMENT_FIELD_TOO_SMALL
+        assert inspector.check_to_self_delay(to_self_delay)[0] == APPOINTMENT_FIELD_TOO_SMALL
 
     # Empty field
     to_self_delay = None
-    assert Inspector.check_to_self_delay(to_self_delay)[0] == APPOINTMENT_EMPTY_FIELD
+    assert inspector.check_to_self_delay(to_self_delay)[0] == APPOINTMENT_EMPTY_FIELD
 
     # Wrong data type
     to_self_delays = WRONG_TYPES
     for to_self_delay in to_self_delays:
-        assert Inspector.check_to_self_delay(to_self_delay)[0] == APPOINTMENT_WRONG_FIELD_TYPE
+        assert inspector.check_to_self_delay(to_self_delay)[0] == APPOINTMENT_WRONG_FIELD_TYPE
 
 
 def test_check_blob():
diff --git a/test/pisa/unit/test_pisad.py b/test/pisa/unit/test_pisad.py
new file mode 100644
index 0000000..fae1d85
--- /dev/null
+++ b/test/pisa/unit/test_pisad.py
@@ -0,0 +1,52 @@
+import importlib
+import os
+import pytest
+from pathlib import Path
+from shutil import copyfile
+
+from pisa.pisad import load_config
+
+test_conf_file_path = os.getcwd() + "/test/pisa/unit/test_conf.py"
+
+
+def test_load_config():
+    # Copy the sample-conf.py file to use as a test config file.
+    copyfile(os.getcwd() + "/pisa/sample_conf.py", test_conf_file_path)
+
+    import test.pisa.unit.test_conf as conf
+
+    # If the file has all the correct fields and data, it should return a dict.
+    conf_dict = load_config(conf)
+    assert type(conf_dict) == dict
+
+    # Delete the file.
+    os.remove(test_conf_file_path)
+
+
+def test_bad_load_config():
+    # Create a messed up version of the file that should throw an error.
+    with open(test_conf_file_path, "w") as f:
+        f.write('# bitcoind\nBTC_RPC_USER = 0000\nBTC_RPC_PASSWD = "password"\nBTC_RPC_HOST = 000')
+
+    import test.pisa.unit.test_conf as conf
+
+    importlib.reload(conf)
+
+    with pytest.raises(Exception):
+        conf_dict = load_config(conf)
+
+    os.remove(test_conf_file_path)
+
+
+def test_empty_load_config():
+    # Create an empty version of the file that should throw an error.
+    open(test_conf_file_path, "a")
+
+    import test.pisa.unit.test_conf as conf
+
+    importlib.reload(conf)
+
+    with pytest.raises(Exception):
+        conf_dict = load_config(conf)
+
+    os.remove(test_conf_file_path)
diff --git a/test/pisa/unit/test_responder.py b/test/pisa/unit/test_responder.py
index cfb0be0..f4704fd 100644
--- a/test/pisa/unit/test_responder.py
+++ b/test/pisa/unit/test_responder.py
@@ -5,15 +5,14 @@ from uuid import uuid4
 from shutil import rmtree
 from copy import deepcopy
 from threading import Thread
-from queue import Queue, Empty
 
 from pisa.db_manager import DBManager
 from pisa.responder import Responder, TransactionTracker
 from pisa.block_processor import BlockProcessor
+from pisa.chain_monitor import ChainMonitor
 from pisa.tools import bitcoin_cli
 
 from common.constants import LOCATOR_LEN_HEX
-from common.tools import check_sha256_hex_format
 
 from bitcoind_mock.utils import sha256d
 from bitcoind_mock.transaction import TX
@@ -21,8 +20,11 @@ from test.pisa.unit.conftest import generate_block, generate_blocks, get_random_
 
 
 @pytest.fixture(scope="module")
-def responder(db_manager):
-    return Responder(db_manager)
+def responder(db_manager, chain_monitor):
+    responder = Responder(db_manager, chain_monitor)
+    chain_monitor.attach_responder(responder.block_queue, responder.asleep)
+
+    return responder
 
 
 @pytest.fixture()
@@ -145,17 +147,19 @@ def test_tracker_from_dict_invalid_data():
 
 
 def test_init_responder(responder):
-    assert type(responder.trackers) is dict and len(responder.trackers) == 0
-    assert type(responder.tx_tracker_map) is dict and len(responder.tx_tracker_map) == 0
-    assert type(responder.unconfirmed_txs) is list and len(responder.unconfirmed_txs) == 0
-    assert type(responder.missed_confirmations) is dict and len(responder.missed_confirmations) == 0
+    assert isinstance(responder.trackers, dict) and len(responder.trackers) == 0
+    assert isinstance(responder.tx_tracker_map, dict) and len(responder.tx_tracker_map) == 0
+    assert isinstance(responder.unconfirmed_txs, list) and len(responder.unconfirmed_txs) == 0
+    assert isinstance(responder.missed_confirmations, dict) and len(responder.missed_confirmations) == 0
+    assert isinstance(responder.chain_monitor, ChainMonitor)
     assert responder.block_queue.empty()
     assert responder.asleep is True
-    assert responder.zmq_subscriber is None
 
 
-def test_handle_breach(db_manager):
-    responder = Responder(db_manager)
+def test_handle_breach(db_manager, chain_monitor):
+    responder = Responder(db_manager, chain_monitor)
+    chain_monitor.attach_responder(responder.block_queue, responder.asleep)
+
     uuid = uuid4().hex
     tracker = create_dummy_tracker()
 
@@ -172,11 +176,10 @@ def test_handle_breach(db_manager):
 
     assert receipt.delivered is True
 
-    # The responder automatically fires add_tracker on adding a tracker if it is asleep. We need to stop the processes now.
-    # To do so we delete all the trackers, stop the zmq and create a new fake block to unblock the queue.get method
+    # The responder automatically fires add_tracker on adding a tracker if it is asleep. We need to stop the processes
+    # now. To do so we delete all the trackers, and generate a new block.
     responder.trackers = dict()
-    responder.zmq_subscriber.terminate = True
-    responder.block_queue.put(get_random_value_hex(32))
+    generate_block()
 
 
 def test_add_bad_response(responder):
@@ -184,7 +187,7 @@ def test_add_bad_response(responder):
     tracker = create_dummy_tracker()
 
     # Now that the asleep / awake functionality has been tested we can avoid manually killing the responder by setting
-    # to awake. That will prevent the zmq thread to be launched again.
+    # to awake. That will prevent the chain_monitor thread to be launched again.
     responder.asleep = False
 
     # A txid instead of a rawtx should be enough for unit tests using the bitcoind mock, better tests are needed though.
@@ -205,7 +208,7 @@ def test_add_bad_response(responder):
 
 
 def test_add_tracker(responder):
-    responder.asleep = False
+    # Responder is asleep
 
     for _ in range(20):
         uuid = uuid4().hex
@@ -235,7 +238,8 @@ def test_add_tracker(responder):
 
 
 def test_add_tracker_same_penalty_txid(responder):
-    # Create the same tracker using two different uuids
+    # Responder is asleep
+
     confirmations = 0
     locator, dispute_txid, penalty_txid, penalty_rawtx, appointment_end = create_dummy_tracker_data(random_txid=True)
     uuid_1 = uuid4().hex
@@ -260,7 +264,7 @@ def test_add_tracker_same_penalty_txid(responder):
 
 
 def test_add_tracker_already_confirmed(responder):
-    responder.asleep = False
+    # Responder is asleep
 
     for i in range(20):
         uuid = uuid4().hex
@@ -274,29 +278,10 @@ def test_add_tracker_already_confirmed(responder):
         assert penalty_txid not in responder.unconfirmed_txs
 
 
-def test_do_subscribe(responder):
-    responder.block_queue = Queue()
-
-    zmq_thread = Thread(target=responder.do_subscribe)
-    zmq_thread.daemon = True
-    zmq_thread.start()
-
-    try:
-        generate_block()
-        block_hash = responder.block_queue.get()
-        assert check_sha256_hex_format(block_hash)
-
-    except Empty:
-        assert False
-
-
-def test_do_watch(temp_db_manager):
-    responder = Responder(temp_db_manager)
-    responder.block_queue = Queue()
-
-    zmq_thread = Thread(target=responder.do_subscribe)
-    zmq_thread.daemon = True
-    zmq_thread.start()
+def test_do_watch(temp_db_manager, chain_monitor):
+    # Create a fresh responder to simplify the test
+    responder = Responder(temp_db_manager, chain_monitor)
+    chain_monitor.attach_responder(responder.block_queue, False)
 
     trackers = [create_dummy_tracker(penalty_rawtx=TX.create_dummy_transaction()) for _ in range(20)]
 
@@ -318,9 +303,7 @@ def test_do_watch(temp_db_manager):
         responder.db_manager.store_responder_tracker(uuid, tracker.to_json())
 
     # Let's start to watch
-    watch_thread = Thread(target=responder.do_watch)
-    watch_thread.daemon = True
-    watch_thread.start()
+    Thread(target=responder.do_watch, daemon=True).start()
 
     # And broadcast some of the transactions
     broadcast_txs = []
@@ -354,13 +337,9 @@ def test_do_watch(temp_db_manager):
     assert responder.asleep is True
 
 
-def test_check_confirmations(temp_db_manager):
-    responder = Responder(temp_db_manager)
-    responder.block_queue = Queue()
-
-    zmq_thread = Thread(target=responder.do_subscribe)
-    zmq_thread.daemon = True
-    zmq_thread.start()
+def test_check_confirmations(temp_db_manager, chain_monitor):
+    responder = Responder(temp_db_manager, chain_monitor)
+    chain_monitor.attach_responder(responder.block_queue, responder.asleep)
 
     # check_confirmations checks, given a list of transaction for a block, what of the known penalty transaction have
     # been confirmed. To test this we need to create a list of transactions and the state of the responder
@@ -390,7 +369,7 @@ def test_check_confirmations(temp_db_manager):
         assert responder.missed_confirmations[tx] == 1
 
 
-# WIP: Check this properly, a bug pass unnoticed!
+# TODO: Check this properly, a bug pass unnoticed!
 def test_get_txs_to_rebroadcast(responder):
     # Let's create a few fake txids and assign at least 6 missing confirmations to each
     txs_missing_too_many_conf = {get_random_value_hex(32): 6 + i for i in range(10)}
@@ -414,13 +393,13 @@ def test_get_txs_to_rebroadcast(responder):
     assert txs_to_rebroadcast == list(txs_missing_too_many_conf.keys())
 
 
-def test_get_completed_trackers(db_manager):
+def test_get_completed_trackers(db_manager, chain_monitor):
     initial_height = bitcoin_cli().getblockcount()
 
-    # Let's use a fresh responder for this to make it easier to compare the results
-    responder = Responder(db_manager)
+    responder = Responder(db_manager, chain_monitor)
+    chain_monitor.attach_responder(responder.block_queue, responder.asleep)
 
-    # A complete tracker is a tracker that has reached the appointment end with enough confirmations (> MIN_CONFIRMATIONS)
+    # A complete tracker is a tracker that has reached the appointment end with enough confs (> MIN_CONFIRMATIONS)
     # We'll create three type of transactions: end reached + enough conf, end reached + no enough conf, end not reached
     trackers_end_conf = {
         uuid4().hex: create_dummy_tracker(penalty_rawtx=TX.create_dummy_transaction()) for _ in range(10)
@@ -473,9 +452,10 @@ def test_get_completed_trackers(db_manager):
     assert set(completed_trackers_ids) == set(ended_trackers_keys)
 
 
-def test_rebroadcast(db_manager):
-    responder = Responder(db_manager)
+def test_rebroadcast(db_manager, chain_monitor):
+    responder = Responder(db_manager, chain_monitor)
     responder.asleep = False
+    chain_monitor.attach_responder(responder.block_queue, responder.asleep)
 
     txs_to_rebroadcast = []
 
diff --git a/test/pisa/unit/test_watcher.py b/test/pisa/unit/test_watcher.py
index a05b6fd..7c1147f 100644
--- a/test/pisa/unit/test_watcher.py
+++ b/test/pisa/unit/test_watcher.py
@@ -1,22 +1,24 @@
 import pytest
 from uuid import uuid4
 from threading import Thread
-from queue import Queue, Empty
+from cryptography.hazmat.primitives.asymmetric import ec
 from cryptography.hazmat.primitives import serialization
 
 from pisa.watcher import Watcher
 from pisa.responder import Responder
 from pisa.tools import bitcoin_cli
+from pisa.chain_monitor import ChainMonitor
+
 from test.pisa.unit.conftest import (
-    generate_block,
     generate_blocks,
     generate_dummy_appointment,
     get_random_value_hex,
     generate_keypair,
+    get_config,
 )
 from pisa.conf import EXPIRY_DELTA, MAX_APPOINTMENTS
 
-from common.tools import check_sha256_hex_format
+from common.tools import compute_locator
 from common.cryptographer import Cryptographer
 
 
@@ -35,8 +37,12 @@ sk_der = signing_key.private_bytes(
 
 
 @pytest.fixture(scope="module")
-def watcher(db_manager):
-    return Watcher(db_manager, sk_der)
+def watcher(db_manager, chain_monitor):
+    watcher = Watcher(db_manager, chain_monitor, sk_der, get_config())
+    chain_monitor.attach_watcher(watcher.block_queue, watcher.asleep)
+    chain_monitor.attach_responder(watcher.responder.block_queue, watcher.responder.asleep)
+
+    return watcher
 
 
 @pytest.fixture(scope="module")
@@ -46,7 +52,7 @@ def txids():
 
 @pytest.fixture(scope="module")
 def locator_uuid_map(txids):
-    return {Watcher.compute_locator(txid): uuid4().hex for txid in txids}
+    return {compute_locator(txid): uuid4().hex for txid in txids}
 
 
 def create_appointments(n):
@@ -67,17 +73,18 @@ def create_appointments(n):
     return appointments, locator_uuid_map, dispute_txs
 
 
-def test_init(watcher):
-    assert type(watcher.appointments) is dict and len(watcher.appointments) == 0
-    assert type(watcher.locator_uuid_map) is dict and len(watcher.locator_uuid_map) == 0
-    assert watcher.block_queue.empty()
+def test_init(run_bitcoind, watcher):
+    assert isinstance(watcher.appointments, dict) and len(watcher.appointments) == 0
+    assert isinstance(watcher.locator_uuid_map, dict) and len(watcher.locator_uuid_map) == 0
     assert watcher.asleep is True
-    assert watcher.max_appointments == MAX_APPOINTMENTS
-    assert watcher.zmq_subscriber is None
-    assert type(watcher.responder) is Responder
+    assert watcher.block_queue.empty()
+    assert isinstance(watcher.chain_monitor, ChainMonitor)
+    assert isinstance(watcher.config, dict)
+    assert isinstance(watcher.signing_key, ec.EllipticCurvePrivateKey)
+    assert isinstance(watcher.responder, Responder)
 
 
-def test_add_appointment(run_bitcoind, watcher):
+def test_add_appointment(watcher):
     # The watcher automatically fires do_watch and do_subscribe on adding an appointment if it is asleep (initial state)
     # Avoid this by setting the state to awake.
     watcher.asleep = False
@@ -121,25 +128,10 @@ def test_add_too_many_appointments(watcher):
     assert sig is None
 
 
-def test_do_subscribe(watcher):
-    watcher.block_queue = Queue()
-
-    zmq_thread = Thread(target=watcher.do_subscribe)
-    zmq_thread.daemon = True
-    zmq_thread.start()
-
-    try:
-        generate_block()
-        block_hash = watcher.block_queue.get()
-        assert check_sha256_hex_format(block_hash)
-
-    except Empty:
-        assert False
-
-
 def test_do_watch(watcher):
     # We will wipe all the previous data and add 5 appointments
     appointments, locator_uuid_map, dispute_txs = create_appointments(APPOINTMENTS)
+    watcher.chain_monitor.watcher_asleep = False
 
     # Set the data into the Watcher and in the db
     watcher.locator_uuid_map = locator_uuid_map
@@ -150,16 +142,13 @@ def test_do_watch(watcher):
         watcher.db_manager.store_watcher_appointment(uuid, appointment.to_json())
         watcher.db_manager.store_update_locator_map(appointment.locator, uuid)
 
-    watch_thread = Thread(target=watcher.do_watch)
-    watch_thread.daemon = True
-    watch_thread.start()
+    Thread(target=watcher.do_watch, daemon=True).start()
 
     # Broadcast the first two
     for dispute_tx in dispute_txs[:2]:
         bitcoin_cli().sendrawtransaction(dispute_tx)
 
-    # After leaving some time for the block to be mined and processed, the number of appointments should have reduced
-    # by two
+    # After generating enough blocks, the number of appointments should have reduced by two
     generate_blocks(START_TIME_OFFSET + END_TIME_OFFSET)
 
     assert len(watcher.appointments) == APPOINTMENTS - 2
@@ -230,7 +219,7 @@ def test_filter_valid_breaches(watcher):
 
     dummy_appointment, _ = generate_dummy_appointment()
     dummy_appointment.encrypted_blob.data = encrypted_blob
-    dummy_appointment.locator = Watcher.compute_locator(dispute_txid)
+    dummy_appointment.locator = compute_locator(dispute_txid)
     uuid = uuid4().hex
 
     appointments = {uuid: dummy_appointment}