Here are some experiments I did with Kinect. By selecting three separate points in space you can define a plane to use as an interaction surface. Kinect is much more flexible than other camera-based approaches for doing this in terms of lighting, camera alignment, etc.
Software: Recording audio and video in sync
It turns out that writing software to record audio and video in sync is not as easy as you might expect. I had to do this for a recent project, and below are some of the issues I encountered, with solutions. I was working on Mac OS X (Snow Leopard) using openFrameworks. I used the openFrameworks movieGrabberExample as a starting point, along with ofxQTVideoSaver to store the video. There are some useful posts on the forums here.
James Patten's blog about interaction design, technology, and life in NYC. 