コンパス（デジタル方位磁針）

A compass app can display direction using your smartphone's sensors.

Besides direction, it can also roughly determine the smartphone's tilt.

Furthermore, by utilizing GPS information, it can determine your current latitude, longitude, and a basic address (prefecture name or city/town level).

This might be useful during Setsubun (the bean-throwing festival) to ensure you're facing the correct direction while holding your Ehomaki (lucky direction sushi roll). (Assuming your hand is free to hold your phone, of course...)