Other than the ultrasonic sensor and the camera? Like, for example, various ultrasonic senors on the sides or infrared sensors, etc.? I had to hook them up via the Raspberry Pi directly, I assume. I don’t own a gopigo yet (can’t order it in Europe right now)
In addition to the US and camera, we have examples of GPS sensors and compass sensors. We should have a list somewhere, we’ll post it. These are Grove sensors. If you’re in Europe, you can buy them all from the same site here: http://www.seeedstudio.com/depot/GoPiGo-Base-Kit-p-2510.html