Other than the part where you'd have a battery strapped to you, this could be interesting to adapt to firefighting scenarios. If you could walk up to a structure and do a calibration so that instead of telling you which way North was it was calibrated to the direction of the face of the building (the "A-side" in most firefighting vocabs) then you could use the feedback from it when inside to know which side of the building you were facing despite being visually cut off and disoriented.