At my house in San Francisco we have a garage, but with a pretty old garage door opener, and I wanted to add some modern functionality to it without a massive new install. A friend of mine introduced me to a smartphone app called Blynk, that allows you to directly control internet connected internet boards, and I knew I had my solution. After experimenting with different boards and different ways of completing the circuit to emulate a button press, I finally come up with this: an Adafruit Feather Huzzah board as the brain of the device, and an optoisolator to actuate the circuit.
There is one button in the app that triggers the garage door to open or close. A reed switch reports whether the door is open or not, and is displayed on the LCD screen in the app. If the door is left open for too long, you'll get a notification on your phone to remind you to close it. If you need to leave the door open for an extended period, you can disable the notifications - they'll be re-enabled the next time you close the door.