Good find, John. There is a detailed PDF in "Downloads", it does look like a fair amount of work was done.
Now please find where to order their servos, kits, or boards...
I've seen something like that done using the open servo controller. It's a fair amount of work, but you take out the old control board, pot, and rotation stop. You put in a magnet and hall effect sensor to determine rotation and the open servo board to position and give feedback via I2C.
Now you have a servo that is continuous rotation with position feedback.
Sparkfun sells open servo boards, but I don’t know if they sell the magnetic sensor.
I found this: http://www.sparkfun.com/products/9014 but the reviews sound problematic at best.