AD: looks like everyone's stumped by the enormity of the idea.
I am a low hour instructor, so don't take my ideas as world-shaking truth. But I can't imagine it would be much use in PPL training, as students are taught to look outside as much as possible, not at the instruments.
Might make unusual attitude flying (& mountain flying) a bit safer for the inexperienced pilot. I doubt that veterans would use it though - they have developed other sensory cues to use.
I imagine light twins doing instrument takeoffs & approaches might use it, but you'd have to ask someone with relevant experience.
Try the other forums?