I have a first edition GP2X [Korean Manufacturer, UK Site]. It's basically a ~200MHz ARM processor with 64MB Ram and SD Card slot handheld device. It was loosely designed to play games and media (videos and music) and run emulators. It runs Linux for an OS. They now sell a Breakout Board which you can plug into it which has 4 USB ports, RS232, Audio and Video out & Jtag. I plan to order one shortly.

My desire is to turn my GP2X into a robot, that is optionally remote controllable from a computer. Getting it on Wifi via USB shouldn't be a problem for me. What I'd like is some advice on where I should look for getting it hooked up to some kind of movable body and what sensors might be appropriate.

Mobility
Initially I'd like it to be able to drive around my basement, which is mostly flat and carpeted, but has two ~10cm steps up to slightly raised levels. It would be nice if it could manage these steps but I don't really see how to do that practically or cheaply.

Sensors
Simple vision should be accomplished with a USB webcam of some sort. But I'm also interested in having better and more sensors, like range/depth sensors, or scanners. Also, I'm interested in Internal Navigation Systems if anything can be done on the cheap (gyros, speedometers, etc).

Power
The GP2X can run off of 2 AA batteries, but that probably won't be enough for everything plugged into the Breakout Board. The GP2X can also run off of 3.3V DC power at 1A. The breakout board also has a power input. And finally the engine/motor will need power. Also, if at all possible, it would be nice if the power solution were easily chargeable via the robot driving into some kind of power up dock station.

Why?
I'm not nearly as interested in the hardware side of this as I am the higher level programming side. I'm much more interested in starting to program something that can drive the robot. Of course thats why I need a robot in the first place. :)

Budget
I don't have too much to spend on this as I'm just about to come to the end of my employment and I am a student. So cheap solutions are a real winner here. More expensive solutions might mean it simply takes me longer to acquire all the parts.

Thank you for your time and help.