Touchless – track colored markers via webcam
Touchless is an SDK that allows users to create and experience multi-touch applications. Touchless started as Mike Wasserman’s college project at Columbia University. The main idea: to offer users a new and cheap way of experiencing multi-touch capabilities, without the need of expensive hardware or software. All the user needs is a camera, which will track colored markers defined by the user.
The video they provide is very enlightening of its capabilities