GestureTek specializes in interfaces that track a user’s hand gestures and body position using a camera. The video below is a concept demo from interface designers TAT.
But GestureTek is building the technology for real (initially to be used by a single user, unlike the multi-user scenario shown in the video). An extra camera module and custom lens is required to track the finger on the projected image. The tracking should be quite accurate, with similar performance to the iPhone touch interface.