توضیحات:

Open source https://github.com/RyanHurst/SlopeFinder

No permissions required.

Easily calculate the slope of a surface, or the slope between you and a point in your camera's view.

Surface mode: Set your device on the surface and your phone will tell you its slope.

Camera mode: Point your device at a point in the distance and your device will tell you the slope of the line between your device and that point.