diff --git a/mqtt_sensord/mqtt_sensord.py b/mqtt_sensord/mqtt_sensord.py
index 5d5c321..f87ebd6 100755
--- a/mqtt_sensord/mqtt_sensord.py
+++ b/mqtt_sensord/mqtt_sensord.py
@@ -33,20 +33,39 @@ def main():
     mqtt = MQTTClient(mcfg['host'], mcfg['user'], mcfg['password'], client_id)
     mqtt_topic = mcfg['sensor_topic']
     print("Connected to", mqtt.host, "with topic", mqtt_topic)
+    mqtt.set_callback(sensorlib.Sensor.run_mqtt_callback)
 
     sensors = []
+    extra_topics = set()
     for scfg in config['sensors']:
         s = sensorlib.Sensor.make_sensor(**scfg)
+        s.register_callbacks()
+        for topic in s.get_topics():
+            extra_topics.add(topic)
         sensors.append(s)
 
+    for topic in extra_topics:
+        print("Subscribe to", topic)
+        mqtt.subscribe(topic)
+
     last_measurement = time.time()
     while True:
+        # handle regular sensor data
         print("Getting values from sensors...")
         for sensor in sensors:
-            data = sensor.gen_datapoint()
-            print(mqtt_topic, data)
-            mqtt.send_data(mqtt_topic, data)
-        time.sleep(max(0.0, time.time() + config['host']['interval'] - last_measurement))
+            if sensor.HAS_SENSOR_DATA:
+                data = sensor.gen_datapoint()
+                print(mqtt_topic, data)
+                mqtt.send_data(mqtt_topic, data)
+            if not mqtt.is_async():
+                mqtt.process_mqtt()
+
+        if mqtt.is_async():
+            time.sleep(max(0.0, time.time() + config['host']['interval'] - last_measurement))
+        else:
+            while time.time() - last_measurement < config['host']['interval']:
+                mqtt.process_mqtt()
+                time.sleep(0.1)
         last_measurement = time.time()
 
 
diff --git a/mqtt_sensord/mqttlib/base.py b/mqtt_sensord/mqttlib/base.py
index b176de6..1a171e2 100644
--- a/mqtt_sensord/mqttlib/base.py
+++ b/mqtt_sensord/mqttlib/base.py
@@ -12,3 +12,6 @@ class MQTTClientBase:
 
     def _connect(self):
         raise NotImplementedError("Connect not implemented")
+
+    def is_async(self):
+        return False
diff --git a/mqtt_sensord/mqttlib/paho_mqtt.py b/mqtt_sensord/mqttlib/paho_mqtt.py
index e92e7d1..2b37642 100644
--- a/mqtt_sensord/mqttlib/paho_mqtt.py
+++ b/mqtt_sensord/mqttlib/paho_mqtt.py
@@ -13,3 +13,12 @@ class MQTTClient(MQTTClientBase):
 
     def send_data(self, topic, data):
         self._mqtt.publish(topic, json.dumps(data))
+
+    def set_callback(self, callback):
+        self._mqtt.on_message = lambda client, userdata, msg: callback(msg.topic, msg.payload.decode())
+
+    def process_mqtt(self):
+        self._mqtt.loop(0.01)
+
+    def subscribe(self, topic):
+        self._mqtt.subscribe(topic)
diff --git a/mqtt_sensord/sensorlib/base.py b/mqtt_sensord/sensorlib/base.py
index 54d048c..77687d6 100644
--- a/mqtt_sensord/sensorlib/base.py
+++ b/mqtt_sensord/sensorlib/base.py
@@ -8,6 +8,8 @@ class Sensor(object):
     hostname = None
     platform = None
     _sensor_classes = {}
+    _mqtt_callbacks = {}
+    HAS_SENSOR_DATA = True
 
     def __init__(self, id, name, type, pin, description, **sensor_conf):
         self.id = id
@@ -45,3 +47,23 @@ class Sensor(object):
             },
             'fields': self.get_data()
         }
+
+    def register_callbacks(self):
+        pass
+
+    def get_mqtt_topics(self):
+        return []
+
+    @classmethod
+    def register_callback(cls, mqtt_topic, callback):
+        cls._mqtt_callbacks[mqtt_topic] = callback
+
+    @classmethod
+    def run_mqtt_callback(cls, mqtt_topic, data):
+        if mqtt_topic in cls._mqtt_callbacks:
+            cls._mqtt_callbacks[mqtt_topic](data)
+        else:
+            print("Unknown callback for", mqtt_topic)
+
+    def get_topics(self):
+        return []
diff --git a/mqtt_sensord/sensorlib/misc_sensors.py b/mqtt_sensord/sensorlib/misc_sensors.py
index 20b38e4..cf3af14 100644
--- a/mqtt_sensord/sensorlib/misc_sensors.py
+++ b/mqtt_sensord/sensorlib/misc_sensors.py
@@ -22,6 +22,24 @@ class FakeSensor(Sensor):
         return {'random': random.randint(0, 20)}
 
 
+@sensor
+class TestSink(Sensor):
+    sensor_class = 'testsink'
+    HAS_SENSOR_DATA = False
+
+    def __init__(self, mqtt_topic, **sensor_conf):
+        self.mqtt_topic = mqtt_topic
+
+    def recvd(self, data):
+        print("I got called! Even with data:", data)
+
+    def register_callbacks(self):
+        self.register_callback(self.mqtt_topic, self.recvd)
+
+    def get_topics(self):
+        return [self.mqtt_topic]
+
+
 @sensor
 class CO2Meter(Sensor):
     sensor_class = 'co2meter'