Onewheel hoverboard

I'm planning to build a onewheel hoverboard for my A-level DT project. https://onewheel.com/ This is pretty much what i'm aiming for. I've got most of it already planned but im not sure how to measure the angle of the board can anyone help?

Two angles to the board. You need a good quality IMU and filter to determine the board attitude.

Looks like fun!