like i mentioned in another comment, do you really need good resolution for gait analysis? You also have people carrying their phones inside the house all the time, so you know what bssid is associated with that coarse movement. and if you have access to their ap/router combo, you can tell what IP that device has and what domains it's been visiting.

Let's say you visit a friend in a different city, the same ISP controlling their router, can use your mac, but even if you turn off your wifi or leave your phone in your car, your volume profile and gait can betray you. how you sit, how you lean, how you turn. I'd wager, if 6-10 distinct "points" can be made out and associated with a person, that's all that's needed to uniquely identify that person after enough analysis of their motion, regardless of where they go in the world.

Imagine if they're not using one AP, but using your neighbors AP as well, two neighbor APs and your own can triangulate and refine much better.

for now ...