When I attended the last TED conference in Long Beach in February 2009, Patricia Maes and Pranav Mistry unveiled a touch sensitive device that allows users to project information onto practically any surface, including the human hand. In their own words: "The SixthSense prototype is comprised of a pocket projector, a mirror and a camera. The hardware components are coupled in a pendant like mobile wearable device. Both the projector and the camera are connected to the mobile computing device in the user’s pocket. The projector projects visual information enabling surfaces, walls and physical objects around us to be used as interfaces; while the camera recognizes and tracks user's hand gestures and physical objects using computer-vision based techniques."
The technology is very impressive. Here is a TED video of Patti Maes explaining this important new invention.