Arduino?

[EricH]

I'm not certain how it was done, but a small R/C type gearbox had the motor directly attached to it. I *think* the ratio was 16:1. Wheel on the output shaft. This was the extension/retraction motor, BTW. If I had to guess, the pulley was removed from the motor and a gear put on. You might also be able to pulley into the gearbox.

For a kiwi drive, you might want to consider a triangular base instead of a circular one.

As another option, go with VEX. Those motors look like small servos. It's also possible to use continuous-rotation servos.