I'm not sure what would work with minimal risk of injury. When I said "stepper" I meant a stepper driving a cable of the sort used to drive a bicycle brake, which would work in either direction, and that driving a spring of known characteristics. A piezo sensor could monitor the pressure and its gradient. However, I've not attempted that sort of thing, and am concerned that piezos measure dynamic pressures better than static.

The size and nature of the probe that contacts the skin would be of real concern, but I'm imagining that the device would take a step around the circumference, then apply pressure to the probes and make the associated measurements, release the pressure, and take another step. I liked the notion of using pneumatic of even hydraulic pressure to drive the probes, but thought the stepper + spring notion might be less costly, massive, and complex.

This approach is, I'm sure, being explored in a number of venues. Money is scarce right now, but, with the conflicts in progress right now, there's work being done to mitigate the damages to our military service personnel.

Your reservations about safety are quite valid. Because there's often nerve damage in traumatic amputations, one can't rely on the amputee to push a kill switch when injury occurs, because he/she might not even be aware of it.

This is not a simple problem to solve.

RE