this is kinda off topic.... But all you'd need is a small r/c car inside the sphere. if you wanted omnidirectional control, setup a small cart that sits on one ball, and drive that ball like a mouse drives it's sensor wheels.
the problem is having the device have any idea what direction it's pointing it. the spehere is free to rotate about it's axis, and unless the inside knows what direction is outside, it won't be able to maintain direction.
To be an AGD supporter, one cannot be an AGD bigot. -Nero
Truth is a complex thing. One must govern by simplicity. -M. Mercier, special counsel to his Majesty for domestic matters. The Brotherhood of the Wolf
"You can't outrun Death forever, but you can make the bastard work for it."