Today virtual projection keyboards are a craze. It is used as modules which can be connected to computers like the cellulon projection keyboard, are used in mobile, PDA's, and small equipments, where space is very small forcomputing.
I, myself am dying to have one. So, inspired by it, I take it as my seminar topic. I was much interested in making one myself also, but I didnt have either the red laser diode projector or the IR laser diode for the detection plane. So, I made a short program in OPENCV to immitate it, by just taking 11 keys.
The text being typed can be seen at the bottom of the video.
I have used color marker on fingers along with blob detection to get these results.