Arduino could process 1-bit video, extracting 240 points on regular NTSC frame. Applying simple math it would be possible to distinguish straight lines, cycles etc.
http://coolarduino.wordpress.com/2012/07/28/visual-navigator-making-it-mobile/
and
http://coolarduino.wordpress.com/2011/12/29/optical-magnet-arduino-project-next-in-a-series-laser-tracking-3d/