Discovered how to make a tilt meter with a compass module! As long as you keep it facing N, it will instead measure tilt on 2 axis. It's sensitive to 1 degree tilt movement from level, only when leveled using servo. All you need is 2 servos $3, one to rotate it to find North, then one to tilt it back about 30 degrees towards South. You could do this the hard way on a fixed object (that doesn't rotate) manually. Stop when the reading changes from 0 either + or -. Do this while the object you want to measure is level, then power off servos. You can adjust the level point L to R (E to W) either with a 3rd servo or by tilting the object you're trying to keep level. If the IC is mounted square it will be level when the reading says so by being unstable bouncing around, without a 3rd servo. If the compass reads 0 you're tilted N. If the compass reads 90 you're tilted W (backwards). If the compass reads 270 you're tilted E (backwards). If the compass reads 180 you're tilted S. If you had 2 of these sensors, it would work on a slowly rotating object. WIth 3 servos you can build a camera stabilization system. It reacts instantly in 10ms.
How/why does this work?