A bubble/spirit level tool, with both a bull's eye level and horizontal/vertical levels, as well as a simple compass. The tool is normally included in my astronomical app (Polar Scope Align Pro) where it has some extra functionality (night mode, watch version), but I decided to release it as a separate free app because I could not find anything with the features I wanted on the app store.

If you enjoy it, there is also an ad-free version with Apple Watch support and night mode called "Bubble Level Watch + Compass".

Basic Features:
-Bull's eye level with surface angle reading, horizontal/vertical levels with angle readings (0.1 degree steps).
-Compass with North heading reading in direction and degrees.
-Works on iOS 8.0 or higher.

Extra features:
-Magnetic declination reading, which shows the offset between magnetic and true north for when you want to use a physical magnetic compass (requires access to your location).
-Accelerometer/Gyro switch in case one of the two works better on your phone (Gyro is default).
-Magnetometer (compass) calibration level display.