The hard part was installing all of the cabling to the doors for it. I ran cat5e to all of the doors, and implemented magnetic reed switches. I also had code to detect a garage door state using two of those switches, so I know when the door is opening, open, closing, or closed. (Binary logic, here). Nice and simple!
If anyone wants to see the code, let me know! (My e-mail username is joe, and my e-mail domain is joe-lewis.com.)