I feel like TI’s micro-controller gets ignored alot by the hobby folks. So pulling up some TI projects I know about like this one. The author modified a Hexbug (radio shack toy) to be controlled by a TI 430MSP. A nice cheap CPU ($5)..and since he is not using the board from TI, just the processor, think about the cost being in the cents. Anyways, the author is just doing a straight brain replacement (oh and upgrades from using cell batteries to AA). This could be expanded upon.
http://buildsmartrobots.ning.com/m/blogpost?id=6401492%3ABlogPost%3A24235