I think he's just using a regular Uno, which has enough pins for 5 or 6 sections. But if you needed more a Mega would work fine. There's not currently any verification. It just sends the signal and hopes for the best. The protocol he's defined for talking to the arduino is extremely simple and one-way. But in the future I can see a place for a two-way communications channel. For example, a bank of toggle switches could be used to do manual section control, while informing AgOpenGPS so it can map the coverage.