I've been thinking about designing sensors during the offseason, but a lot of my projects would involve a stamp or pic to process data. Is this allowed? If a stamp is allowed, what's to stop us from putting a PC onboard

(other then weight)? What about sensors, would any of the following be against the rules:
Sonic Range Finder
"Compass" sensor
Vision tracking with onboard PC!
etc.
I've been unable to find any rules regarding them, so I presume I could use any sensor/extra processor I want, right?