This project enables the retrofitting of a single touch experience with practically NO EXTERNAL HARDWARE. All you do is mount your webcam off to the side facing the monitor, and software will automagically do the rest.

The basic concept is that almost all screens are shiny. Even matte ones. Try it, touch your monitor while looking at it from the side (like a 20 degree angle from being parallel). Behind your finger you can see a slight reflection, and notice that the reflection only "touches" the real finger when it's in contact. So what this does is track the position of the finger (simple) and looks to the immediate right to search for a reflection. If it is there, then it's sensed as a touch, or else it's nothing.