Hand tracking screen

Do you have an idea that doesn't fit any of the other challenges? This is the place for you, whether you want to design and develop an app, create a data visualization, hack on an Arduino... or anything else you can think of!

The idea of using touch screens is a bit costly. My idea is to use simple projectors and a transparent material that reflects the image from the projector but at the same time you can see right through it. A meter away from the screen is a camera that is operated by a prgram that follows the users hand and thus controling the screen itself.

USB camera, transparent plastic, wooden frame.