The luminaire may comprise a communications module 205 for wireless communication with other devices. In particular, for the purposes explained below the communications module 205 is configured to receive indication messages from other devices. However, it is reasonable to assume that the luminaire should both be able to learn from transmissions of others and be able to make transmissions to allow others to learn. Consequently the communications module 205 may also be configured to transmit indication messages, and the controller 201 may be configured to make the communications module 205 transmit an indication message in response to a triggering local input signal. An indication message is typically a message that provides some kind of indication of the status of the device that transmits the message, so it can also be called a status indication message. The status may be for example a static status like e.g. “l(fā)ights off”, “l(fā)ights on at full power”, “l(fā)ights on at N % intensity” (where N is a number between 0 and 100); or a dynamic status that involves action, like “in the process of turning lights on to N% intensity” or “in the process of dimming lights to N% intensity”; or just an announcement of observations made, like “movement observed”, or the like.