The key thing to making this all work is really the software that converts the detected blobs of light where your fingers are into awesomeness...of course a good soundtrack also makes a huge difference. I used touchlib
which basically just worked out of the box. There is a calibration utility which saves results to a configuration file that is shared among the other apps. I also downloaded some Flash apps, including the light-box shown in the video. These interface with touchlib via OSC, a neat protocol for relaying timestamped events which should provide a good starting point for building your own apps.