I may do the same, I bought a bunch of the sensor breakouts before getting the Breakout garden board. I have one of the trackballs. Plugged in at the moment for testing. I want to eventually mount it in my SmartiPi case where the camera would normally go. Having trouble getting it to work on boot up via crontab though. I may try the evdev-mouse.py instead of the mouse.py and see how that goes.