Moving eyes behind a painting... Reminds me of one of those old 40's or 50's movies.
One of my nephews said he had the idea of doing a painting with moving eyes that would follow a person walking past. He planned to put it at the bottom of a dark stairway, such as going down into the basement.
This is the circuit I gave him to accomplish it. It is a simplified way without requiring elaborate face recognition, etc. It just locks onto any object nearby and follows it with the eye movement. It only gives the illusion that it is following the person, but that should be sufficient for the effect he wants. It would be necessary to hid the ultrasonic uint in a way that it could not be seen, as it has to move back and forth to spot anyone nearby.
Also, I showed using a 28X2 controller, but a smaller one would do the job. —Even an 8-pin one could do it.
(I specified the 28X2, because I just happen to have some 28X2 picaxes laying around and considered he might ask me to send him the parts he needed to build it.)
Anyway, I thought I would post it here as well. It might give someone some ideas for their robot.
ADDED (13JUN2012): Here was an idea I had to hide the sensor by making a special little "Name Plaque Holder" with the sensor and servo inside (Servo attached to inside top of box, so sensor would be closer to the bottom and all inside painted flat black. Padding to be added as needed to quiet the servo.