Ever felt the need to urgently check the leveling of a surface but didn't have a spirit level handy or lazy to download an app? Then this is just for you. If you Google 'bubble level' or 'spirit level' on your phone's browser or the Google Search app, you will instantly get a spirit level that works with the magnetometer on your phone, assuming it has one. You can keep a device flat on its back to check overall level or sideways to check horizontal tilt. Do keep in mind your phone's magnetometer needs to be properly calibrated for this to work and that any bumps on the back or side (cameras, buttons) will automatically unlevel the phone and mess up your reading. For any serious work you should be using an actual spirit level since the ones on phones could go whack for a number of reasons but for a quick, casual check this should work...
Source: http://www.gsmarena.com/google_bubble_level_to_get_an_instant_spirit_level-news-15698.php
