I'm working on building one of these: http://hackingroomba.com/projects/build-a-roomba-bluetooth-adapter/
I have all the parts except for the Bluesmirf module (DIYbin.com hasn't shipped yet despite being ordered over a week ago) and it should all fit into a mini-altoids tin. I'm using an old PS/2 mouse connector with the plastic tab removed to connect to the roomba SCI. On the other side of the bluetooth connection will be my android phone with the roomba touch-drive app.
What do you all think?
Edit- Also the parts are so small that I'm pretty sure you could fit it under the hood (on a 400 series roomba at least). You would just need to tap into the RX and TX wires in the SCI, in addition to GND. Then you would need to find +5V somewhere on the board or use a 7805 voltage regulator like the DIY rootooth has.