I have some GPS modules I will swap for sensors
These are Pharos GPS-360s that came with MS Streets but they have been hacked for use with micro-controllers. They are breadboard ready and I will provide info on pinouts and even an Arduino sketch to read them. They are accurate, especially in motion, but tend to report they are jumping around in a small area (maybe 15' under an open sky) when at rest. It is still the "right" small area, but for my application I need ridiculous accuracy. Anyway, I have 3 of these to trade.
Breadboard not included. If you look up FTDI you can figure out the pinout from this picture (I will provide more specific info; that's just an FYI in case you get your hands on one some other way).
I would like to get some sensors to try. Ultrasound or infrared would be preferred but I would be interested in other things as well.