I was reading a cool blog and saw: http://www.statusq.org/archives/2006/11/20/1217/ In that post is a video of Andy Wilson of Microsoft Research. His interface is very simple and cool. My one thought is, when is Apple going to make the in-built iSight movable so you can point it down and use it with something like this? It'd be dead simple to just hang a USB web cam over your monitor, but far less elegant.
This is a cool idea to come out of MSR. I've seen other stuff form there and the MSR does some really neat stuff. ANd I love the t-shirt Andy is wearing in the video.