My recent post on the DJ camera-tracking controller helped me remember another very cool camera-based tracking system that I have buried in my bookmarks. CamSpace is a product by Cam-Trax Technologies.
A three year project practically all undertaken by one individual, CamSpace is a freaking awesome look into what could be the future of gaming and user interaction. So far, the technology works with any game using any webcam (95% officially supported as of June).
Make sure to watch the end of the video when they demonstrate shooting simply with taped up fingers.