Thanks for the responses. CMUcam has possibilities! The roborealm of course would work almost perfectly except I want the logic to reside on my microprocessor (not a local computer).
As for Ran's questions...
1. Yes, the camera can spin until it finds the object
2. Strict accuracy is not needed; maybe 10 degrees of "give" or "wobble"?
3. I was hoping for a everything except the camera under $150-200.
4. Yes, infrared was my first thought (e.g. if object is human, but the signature isn't unique enough with multiple targets)
5. Very little. Just imagine a person (or dog, etc) walking around a large room. Very little vertical movement.
6. I'm not worried about mirrors, but as I mentioned, there WILL be many hot items in the room which would make infrared problematic (unless the sensor was smart enough to detect a human vs other hot objects).
My first thought was two receivers (one on each side of the unit) which could calculate distance to the tracked object with...what? What about RF? What about using the CMUcam and "programming" the unit with the object's color? Is there a cheaper solution for this "blob color programming"? What about some sonic emitter attached to the object and a microphone or two on the unit which tries to maximize the signal?
Is there some solution involving laser beams and sharks?
Anyway, thanks in advance for all input!!