If you have an iTach IP2CC or WF2CC from Global Caché connected to your garage door opener, you can use this app to open and close the door from your iPhone.
The app will, when launched, detect all iTach units on the subnet it is connected to. You will then be able to configure each of the three ports on any IP2CC or WF2CC unit as "pulse" or "on/off".
Note that your iPhone needs to be on the same subnet as the iTach unit to detect it. When detected and configured, the app will remember the unit and you will be able to control it as long as there is a non-NAT route from the subnet you are currently on and the iTach.