Mr. Steve Beyer and I have made some good progress on interfacing the gumstix connex to the iRobot Create.  Since the gumstix will be communicating serially with the iRobot, we had to do a bit of investigating to figure out the name of the STUART and the exact port on the robostix expansion card.  Here's proof that we can send a serial signal from the gumstix connex STUART using the linux command:

% echo "hello" > /dev/ttyS2