Ringing Bells is the first Android app I wrote.

It is very simple to use, shake the phone and hear the bells ringing.
Get it on Google Play, it’s free.

With respect to Android development, writing this apps I learned:

• how to get values from sensors, and how to use them (e.g., recognizing shakes);
• to respect the Android app life cycle, and specially how to avoid to consume CPU and battery when the app goes in background;
• how to use an arbitrary event (shake) to reset the timer that puts the phone in stand-by;
• how to play sounds, also modifying their pitch;
• a first experience on creating a GUI on Android;
• how to properly package an app for Google Play;
• update: properly setting the required API level (I already released a new version of the app, identical to the previous one, just with a lower the minimum Android version required so that a friend with Android 2.2 can install it).

Download the Ringing Bells source code (GPL).

The bell sound comes with a CC license from Dan Oberbauer.