Why not use some real fast DC motors, coupled to a gearbox with a huge ratio and big ass wheels ? Maybe you could use a laser cut encoding wheel with a IR couple diode to get the exact number of degrees your wheel rotated.
mem : you're talking about the sensor from the microsoft mouses that benoit rousseau hacked ?
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1154816099
That might work