Tasker. Makes your smartphone into a friggin genius phone.

For example: If I plug in my phone and lay it face down after 840pm at home, Tasker checks my next alarm and says it out loud, turns off all my lights, advises me if there are any doors/windows open or unlocked, locks both of my cars, sets my phone to silent and dims my phone's screen.

When my phone loses Bluetooth connection to my car, Tasker gets my location and saves it to my home screen (I travel a lot and airport parking lots are big). Tasker also sets my volumes to levels appropriate to where I am (low at home/loud at work). If I am home, Tasker locks my car about 45 seconds after the disconnect.

As I leave a 3km radius of my home, Tasker checks if there are any doors/windows open or unlocked at home and announces any issues.