I just completed a project to build a smartthings connected garage door opener and it’s working great!
My goal was to build something that was as simple as possible, and I ended up basing a lot of the code off of this [RELEASE] Absolute Simplest ESP8266 Smart Blinds, no mqtt, rest, bridge, or broker, just your board and your hub and just adapting it for a push button instead of an open/close action.
I used an esp8266 nodemcu with a 5v relay connected normally open directly to the terminals on the back of the garage door opener unit. Smartthings triggers the relay which completes the circuit, ‘pushing’ the garage door opener button.
The reason I wanted this was to be able to close my garage door remotely in case I left it open accidentally. I have a tilt sensor on the door already which alerts me if it’s left open for too long, but until now there was no way to operate the door without driving back home again.
If people are interested I can post the code later, I need to clean it up a bit first though.