Hey Steve, if getting the spybotics to drive in a straight line is proving challenging, consider equiping it with a MEMS rate gyro, interfaced via I2C out of a PSoC. The voltage delta out of the gyro is proportional to the turning rate and signed, so it shouldn't be too difficult to do some simple self-calibration and control.

I should have some more time this weekend to continue exploring the PSoC Mini Dev Kit.