The author uses an app with it called Cayenne. I haven’t heard of it but it sounds interesting. Overall the RPi zero is used to open/close the door and keep the state of the door with one magnetic sensor. The author is using an 8 channel SainSmart relay, which seems like overkill to me, but for $6 I guess its not that bad. Also I don’t understand what the 2nd USB port is for. One is power, but no idea what the 2nd one does.
http://www.instructables.com/id/Garage-Door-Opener-From-Smart-Phone/
relay:
Cayenne app