SmartThings SmartApp to send a push notification if the garage door is open too long.
Has options to specify the amount of time before alerting, and to mute the alerts.
I wrote this SmartApp to specifically work with my GoControl/Linear GD00Z-4 Z-Wave Garage Door Opener, as I found the original Garage Door Monitor template in the SmartThings templates worked with a different kind of sensor (ThreeAxis). However, it should work with any SmartThings contact sensor device.