Abstract: A kit of parts is provided comprising a light and/or loudspeaker fitting for a smart home system. The light and/or loudspeaker fitting comprises a lighting component and/or a loudspeaker; a sensor data input interface; and a processor. The kit of parts further comprises a sensor module comprising a sensor data output interface; and one or more sensors. The light and/or loudspeaker fitting and the sensor module comprise complementary fastening means configured to detachably couple the sensor module to the light and/or loudspeaker fitting so that the sensor data output interface of the sensor module is in communication with the sensor data input interface of the light and/or loudspeaker fitting when the sensor module is coupled to the light and/or loudspeaker fitting, so as to form a sensor interface between the sensor module and the light and/or loudspeaker fitting.