15 years or so ago I was involved in a clinic that used small ( 1.5 metre square) pressure sensitive mats to do quick gait analysis. The mat and software were expensive for the time but not exceptional. The resolution of pressure would have been more than enough to distinguish people and with the time invested I bet it could have a reasonable ability to classify the activity with reasonable margins of error. Given how expensive some of the freestanding buildings for public toilets have been locally it would not be a huge increase in budget.
Of course just because it is possible does not mean it should be done.
Edit: just did a quick search and mostly came back with the in shoe insert pressure sensors. The obvious solution is to make everyone have in shoe sensor so we can solve this … problem?
