The Nintendo Wiimote contains a very special Infrared camera that not only senses sources of infrared light, but tracks the coordinates of up to four separate point sources at high frame rates.
Using a microcontroller to interface with the camera, retrieve the four objects, and report their coordinates to this application which plots the objects in realtime.
You'll need to install the RXTXcomm native library for this to work. (DLL, jnilib, etc)
Demo video: https://youtu.be/ymi5W1wVJ6U