The only reason I would consider a motion tracking web cam is because you don't need Roborealm and you don't need to write any code. The video processing is in the driver. I would probably still have to hack the pan/tilt servos to get the track control info. In any case it's not a preferred option for me, because I don't really want a PC in the loop.
As an aside - I used to do pixel level processing back in the days of the 386 (circa 1990), with no special packages. I used a cheap frame grabber and simple Quick Basic programs in DOS. Very easy to do frame difference, object detection, edge filtering, texture analysis, etc. Of course back then we didn't need no stinkin Windows, GUIs, VB, etc.