This is a computer mouse that communicates with the computer using light as the form of energy, rather than electricity. (There is no category in this contest for this device).

The Light Mouse is a passive device with few parts, making it inexpensive to manufacture.  The Light Mouse is not to be confused with an optical mouse which requires a cord or recharging.  

Light enters the mouse and makes several reflections to enter a dark chamber where it is diffracted into colors which are reflected and focused at the slots of chopper wheels, and then retroreflected back out of the mouse to the computer.  

Features of the Light Mouse:

• From the Light Mouse (however, are relocated in the computer).
• Most of the optical components used in the Light Mouse are molded as part of the housing, reducing costs.
• The Light Mouse controller (light source and detectors) is compatible with Mac, PC, etc..
• The Light Mouse emits no electrical radiation., evading hacking.
• No battery, therefore:
  a. Reduced cost of the mouse.
  b. Reduced weight and fatigue.
  c. No batteries to recharge or replace.

Retro-reflectors return light back to the source, like animal eyes or a bicycle reflector.  In the pictures above, animal eyes retro-reflect the photographer's light back to the camera.  When the animal blinks, the return signals turn off and on cleanly creating square waves.  This Light Mouse is an "animal" that blinks in five colors.

U.S. Pat. 6,111,563
U.S. Pat. 6,344,846
https://www.hineslab.com/optical-projects/non-electrical-light-mouse