Although this isn't too evil..

I am trying to make a system to control spotlights like in theatres for my A2 computing project.

I've been trying to find a method of sensing the object to focus on, i.e. what co-ordinates on the stage to look at. Most proximity sensors either sense in a direct line or sense the presence of something but not the distance. What I had in mind before I started searching was a small device strapped to the performer and 2 sensors (x and y axis) detecting the distance from the device and from that you could work out the co-ordinates. Anyone know where I could get this device and sensor style of component?

-Jack.

Probably a camera, or pair of cameras, plus some image processing software is what you need.