I saw one being developed. You have to calibrate it for every surface. The surface has to be solid, no metallics or clears. Its useless, but yes, very cool. Unfortunatly, that has been out for years, and the cool factor is mostly gone.
soon .... you'll no longer be using your eyes.....it will just be cerebrally holographed apon your minds eye.... and your fingers will be virtual representations of themselves where as your real fingers will have an interface of tactile response that the virtual fingers track.