Storing & getting the device orientation (yaw, pitch, roll) when taking a photo
This is one of those problems that I believe requires a documented standard:  the same reason every platform trivially accesses the GPS location of a photo is because of EXIF and it's standardized tags.

EXIF is not user-extensible, and side car files are too namespace-y (proprietary).

Unless I'm wrong about there not being a standard place for Euler angles or even the quaternion that establishes device attitude.