While touch sensing is commonplace for single points of contact, multi-touch sensing enables a user to interact with a system with more than one finger at a time, as in chording and bi-manual operations. Such sensing devices are inherently also able to accommodate multiple users simultaneously, which is especially useful for larger interaction scenarios such as interactive walls and tabletops.
http://cs.nyu.edu/~jhan/ftirtouch/
Touchlib is our library for creating multi-touch interaction surfaces. It handles tracking blobs of infrared light for you and sends your programs multitouch events, such as 'finger down', 'finger moved', and 'finger released'. It includes a configuration app and a few demos to get you started. It interaces with most major types of webcams and video capture devices. It currently works only under windows but efforts are being made to port it to other platforms.
http://www.whitenoiseaudio.com/touchlib/
