this is pretty dang sweet. its about the coolest thing ive done with my arduino in a long time.
basically I used the Face tracking demo that comes with opencv and modded it till it ran a little faster then i made it so it would send info about the position of the persons face over the serial port.
UPDATE: 9/8/2010
finally the instructable has came to fruition !
the guide and code can be found here:
http://www.instructables.com/id/how-to-build-MACKRA-a-serb-variant/