It ran through my mind when I discovered the iPodLinux project last year (a very personal discovery, but iPL has been going on at least since 2003), that the iPod would be a very powerful brain for an intelligent robot (and I wasn't alone in pondering this). With CPUs running at 80MHz, plenty of storage space for robot learning, and a serial I/O (Gens 1, 2 and 3), it would be possible to control a robot with the Apple music player. In fact, the Roomba is already electronically compatible with the iPod serial port (Gen 1, 2 and 3), and its hacking is officially backed by iRobot. Wouldn't it be fun to start experimenting iPod-brained robots?
Sparkfun, one of my favorite outlets for sensors and ICs, has a few related iPod and Roomba development items: iPod Console and Roomba RS232 adapter, but they wouldn't be necessary once the iPod communicates directly to the Roomba.