diff --git a/include/sensor.hpp b/include/sensor.hpp
index 0f90118..dc91fc1 100644
--- a/include/sensor.hpp
+++ b/include/sensor.hpp
@@ -77,6 +77,12 @@
     size_t errCount;
     std::unique_ptr<SensorInstrumentation> instrumentation;
 
+    // This member variable provides a hook that can be used to receive
+    // notification whenever this Sensor's value is externally set via D-Bus.
+    // If interested, assign your own lambda to this variable, during
+    // construction of your Sensor subclass. See ExternalSensor for example.
+    std::function<void()> externalSetHook;
+
     void updateInstrumentation(double readValue)
     {
         // Do nothing if this feature is not enabled
@@ -172,6 +178,12 @@
             // check thresholds for external set
             value = newValue;
             checkThresholds();
+
+            // Trigger the hook, as an external set has just happened
+            if (externalSetHook)
+            {
+                externalSetHook();
+            }
         }
         else if (!overriddenState)
         {