Garage door openers are simple enough when it's just a button, but if you want something more high tech, Instructables user MegunoLink shows off how to build a garage door opener you can control with your smartphone.
MegunoLink's build uses a network capable Arduino, a relay board, a few cables and wires, and a power supply. From there, you'll just compile the code onto the Arduino and you can then access your garage door from anywhere. The end result is a pretty straightforward system where you'll enter a password into your phone that opens the garage door. Head over to Instructables for the full guide.
Arduino WiFi Garage Door Opener | Instructables