You can accomplish something very similar with an electrical gyro, too, if you're just interested in assisted turning. You should check out the MEMS gyroscopes on sparkfun.com.
We used one in a project at IIT where we performed controld drifts with an RC car:
http://mechatronics.iit.edu/index.php?n=Fall08.Group2.
The gyroscope we used was the MLX90609-E2:
http://www.sparkfun.com/commerce/pro...oducts_id=8336. It measures up to 300d/s across 5V.
The thing is, the gyroscope is for heading only and won't detect tilt. We coupled it with an X/Y accelerometer for complete control of the vehicle.
I guess my question would be, why spend all the weight developing a large mechanical gryo?