To Ben -
Count me in among the folks interested in the 3Pi. Like some of the others have mentioned above, I'd to use the 3Pi as a expandable base. One of the comments you made earlier has me intrigued:
...you have the option of using LCD pins for I/O if you remove the LCD.
Judging by the 3Pi picture and the data sheet for the 8X2 display, it looks like you're using 11 pins?
I'm thinking:
Remove the LCD, and add some additional sensors to the base
Add a second platform with another AVR & the previously removed LCD
And maybe an xbee radio.
Instead of using the serial pins, utilize the 3Pi as an SPI Slave.
I look forward to checking out the schematics as soon as they're posted, to determine approximately how much power the 3Pi is using, and how much might be left over.
Any thoughts?