A few comments… the recommended GoControl in the FAQ of the OP was trash, unfortunately. I got it at a deep discount for like $50 at Staples and still returned it as the range was worse then the GoControl door sensor which is hanging in the same garage, about 70 feet away from the ST hub and obviously many walls and stucco in-between. However, I do have a range extender on the last wall of the house which does help the door sensor but failed to help the GoControl garage kit.
I stuck to my original configuration of my custom HTTP Device Handler using a Raspberry Pi and a relay which is spliced/soldered onto the back of the garage wall panel. You can also use a WeMo to trigger a car type of relay. I may change this up to use a tiny ESP8266 Arduino-like board based on @Casper’s project. This way I can also trigger the garage light not just the garage door considering I have reliable WiFi in the garage. I’m also doing this in my gate box but using a RPi and a power-line Ethernet adapter instead of flaky WiFi.
Reason for splicing is because it’s not just a simple control panel because LiftMaster/Chamberlain use it for multi-function purposes, that means shorting the two wires is useless. You must solder to the back of each momentary button of the panel. BTW, my older garage door motor is NOT MyQ capable so obviously this is the old-school technique but it’s reliable and has much more capability and potential for future enhancements.