A wearable device and external reader is provided for herein. In some embodiments of the present disclosure, the wearable device or the reader is configured to receive a level of radiant energy, detect a change in the received level of radiant energy, determine that the detected change in the received level of radiant energy is indicative of a predetermined pattern of received radiant energy, and responsively operate (or cause to be operated via the external reader) one or more external devices.
