I was looking for a way to have a robots head follow something or someone around. I've seen some robots that have a servo with an IR-sensor on top that finds either the left or the right edge of anything you put in front of it. I toyed around with that, but I got frustrated with a few things.
If you follow the left edge of an object, the robot allways seem to look slightly left past the object instead of in the middle. Also:When the edge is detected, the servo goes from left to right and back between detecting the object and looking past it.