This is a wacky little project. Basically you train a webcam to follow a spot on a piece of paper. Then you set “hotspots” on the image and assign commands to each hotspot. When you aim at the spot you basically “press” a button.
Why would this be useful? You could potentially create a presentation system with this or help a handicapped person type with it. It’s also really cool. The whole project includes source code for Linux.
Laserspotcam is a software I wrote to control xmms using a laser pointer by pointing defined areas on a wall.
The software monitors the wall for the presence of a small spot using a webcam. When the spot appears somewhere, if it is inside a defined hotspot, the appropriate command is executed.