Measure everything that vibrates, shakes or moves. Or why not an actual earthquake?
This program Taking advantage of the built-in accelerometer in your iPhone, Multi Seismometer detects and visualizes any vibrations and moves of the iPhone,calculate the resulting energy and provide alarm. So, why not using this excellent feature to help your iPhone self-protected like a car when combined with an alarm? Or another great application is to test how smooth the car is on a test drive. And of course, why not earthquake detection as well?