A smart garage-door controller is an add-on to your present garage-door opener,  and allows you to control the door from anywhere through an app on your smartphone, tablet, or computer. 

Good smart garage-door controller work with most garage door sytems including  Chamberlain and LiftMaster. They are simple to set up. 

The best smart garage-door controller for normal use: Chamberlain MyQ Garage (easy to set up, compatible with most garage doors)

The best smart garage-door controller upgrade: Gogogate2 (advanced options, direct camera integration, geofencing, and voice control with IFTTT and Amazon's Echo.)

The best smart garage-door controller for the home-automation enthusiast: GoControl/Linear Z-Wave Garage Door Opener Remote Controller (ability to pair with many smart-home systems)