I have wanted to make an infrared-based chording keyboard. Using an infrared camera, monitor the velocity of the five brightest points and consider a fingertip

I have wanted to make an infrared-based chording keyboard. Using an infrared camera, monitor the velocity of the five brightest points and consider a fingertip contracting to be keypress. Throw a small infrared LED into the front of a smartphone and a forward facing infrared camera and voila, smartphone chording keyboard, without taking up any screenspace.