Nice. I am working with arduino a lot lately. I just built from scratch a 2-axis pan-tilt motor system controlled by an arudino mega, controlling stepper motors taken from old 3d printers. I can put a laser pointer on it too, and aim at things on the other side of the room with a 1/4 of a degree accuracy. I built it to have a high-speed mode and a high-precision mode and it has a button to switch between them, and each motor is controlled by a potentiometer with a guitar volume knob on it. It turned out pretty well and I made it in about 2 days.

It's strong enough with the NEMA 17 stepper motors I think I'm going to try attaching my DSLR to it with the zoom lens. Then I can mount it on a tripod and basically have a perfectly accurate digitally controlled telescope. I bought an adapter to attach the DSLR camera to the stepper shaft yesterday, so hopefully I can get it working soon.

I might also try to use it as a sun tracker to keep a fresnel lens in focus as the sun moves. It's exciting to think you could make like a walking chair or anything you want if you had powerful enough stepper motors that could lift hundreds of pounds. Controlling stepper motors directly with arduino code opens a lot of doors, I'm glad I finally figured out how to do it.