Optical communication for body mountable devices

A system comprising:

• one or more optical emitters that emit light;
• a transceiver coupled to receive input data from a data network and coupled to selectively modulate the optical emitters to transmit optical data via the light, wherein selectively modulating the optical emitters is in response to the input data;
• and
• a body mountable device adapted for wearing on a human body or implanting into a human body, the body mountable device including:
• a photodetector positioned to receive the optical data;
• processing circuitry configured to initiate an action in response to receiving the optical data from the photodetector;
• a memory coupled to the processing circuitry, wherein the optical data is encrypted and the memory stores a decryption key accessible to the processing circuitry for decrypting the optical data;
• and
• a sensor coupled to the processing circuitry, wherein the action comprises a measurement, and wherein the processing circuitry is configured to initiate the measurement with the sensor in response to the optical data and to store the measurement in the memory.