Very easy to install on your garage door (see second picture - connect the hub to an electric outlet, restart your Wifi router, and stick sensor on your garage door). Once you download the Chamberlain app, You can check from your cell phone whether you have closed your garage door. You can remotely close/open your garage if you have left it open after driving away from home. I changed my garage door motor, which has this new feature as a built-in, thus I no longer need this device. I have two box sets. Each box set is $25. The extra sensor (third picture) is $10 - this was from my double garage. One hub can support two sensors. Pick up from Terra Nova.