Perhaps you've seen Johnny Lee's Minority Report-ish Wii Remote hack. Being able to track fingers in mid air is pretty impressive, but his newest Wii Remote hack could actually save someone thousands of dollars.
The digital whiteboards you'd see in boardroom presentations and classrooms are really expensive, but Mr. Lee's hack will give similar results for less than $100. This solution uses the Wii Remote's infrared camera to track pens that emit infrared light. By pointing a Wii Remote at a projection screen or LCD display, a sort of whiteboard or tablet display can be created.
In the video demo of this hack, Johnny is able to freely draw and control a computer with his DIY light pen, which is basically a hollowed-out Bic pen with a infrared light inside. The only other requirements are Lee's custom code and a Bluetooth link from Wiimote to PC.
I've seen some impressive hacks in my day, but being able to squeeze the functionality of a digital multitouch whiteboard out of a $40 game controller is truly amazing.
[Via the always awesome Ars Technica]