I wanted a SmartApp that would close the garage door if no activity was detected over a period of time using a motion sensor. So this is my initial cut at just that. After X amount of mins after any specified garage door is opened or after the last motion event is detected, the garage doors will be closed. This prevents the garage door from closing on yourself, your kids, your car reversing, etc. but still allows for the garage to close after a specified amount of time.
It supports multiple garage doors and multiple motion sensors. I wrote it to be extremely lightweight.
This smartapp works great for my kids who are playing out in our alley constantly but forget to close the garage when they go on a bike ride or similar.