Shadow Cam transforms your camera to capture light and shadows in images!!!Light and dark regions appear stunning with this app!
This would require somehow very carefully calibrating the alignment of your camera mount with the alignment of your IMU.
It would also require very careful calibration of your camera motion.
After thinking about it some more, I'm not sure if this would be enough information to correct for IMU errors on the fly. ) How would you separate out if your errors are due to roll, pitch, or yaw and in what proportion?
But maybe if it's an extra vector of information you can work into your filter you could do something helpful with it?
And then you'd probably want some sort of image processing algorithm that could reliably locate your shadow (or whatever object you are pointing at) in the image.