Grid Inclinometer

It is a bubble level and spirit level app alike which uses a smart phone with built in sensor.
Hold your phone flat horizontally or vertically adjusting the red line.
Frames, constructions, carpenter, You can use this leveler app anywhere.
It is easy to use.

Note:
Some phones will give different sensor readings based on the hardware used by the manufacturer.
And Some phone having a bad sensor(or error sensor) will show inaccurate result.