Mike Wasserman had one of the coolest college projects ever. He The SDK can be found over at Codeplex @ http://www.codeplex.com/touchless. It allows you to do a multi-touch experience with your current generation hardware.
The SDK does have a full blown demo so you can test out what you see in the video. All you need to run this is .Net 3.0 and a web cam. Imagine this combined with the WiiMote lib.