diff --git a/src/interfaces/sensor.hpp b/src/interfaces/sensor.hpp
index dbeb158..07c7897 100644
--- a/src/interfaces/sensor.hpp
+++ b/src/interfaces/sensor.hpp
@@ -1,5 +1,7 @@
 #pragma once
 
+#include <chrono>
+#include <memory>
 #include <ostream>
 #include <string>
 #include <string_view>
@@ -8,6 +10,8 @@
 namespace interfaces
 {
 
+class SensorListener;
+
 class Sensor
 {
   public:
@@ -28,11 +32,17 @@
             return std::tie(type, service, path) <
                    std::tie(other.type, other.service, other.path);
         }
+
+        inline std::string str() const
+        {
+            return type + ":" + service + ":" + path;
+        }
     };
 
     virtual ~Sensor() = default;
 
     virtual Id id() const = 0;
+    virtual void registerForUpdates(const std::weak_ptr<SensorListener>&) = 0;
 };
 
 } // namespace interfaces
diff --git a/src/interfaces/sensor_listener.hpp b/src/interfaces/sensor_listener.hpp
new file mode 100644
index 0000000..9a2f0a2
--- /dev/null
+++ b/src/interfaces/sensor_listener.hpp
@@ -0,0 +1,19 @@
+#pragma once
+
+#include <optional>
+
+namespace interfaces
+{
+
+class Sensor;
+
+class SensorListener
+{
+  public:
+    virtual ~SensorListener() = default;
+
+    virtual void sensorUpdated(interfaces::Sensor&, uint64_t) = 0;
+    virtual void sensorUpdated(interfaces::Sensor&, uint64_t, double) = 0;
+};
+
+} // namespace interfaces