It's a research paper by university students. They're just showing ways the existing technology can be harnessed. What you don't know can hurt you. Moreover, you can't harness any phenomenon you don't know about, in the event that it could provide you with some benefit. It's also plausible that future wifi standards could be adjusted to make this sort of thing a lot more difficult.why do we need this... what part of this technology benefits the end user in any way.
The paper suggested it could be used to monitor elderly persons, to ensure they haven't fallen or remained immobile for too long. They also highlight that it can work in the dark.
Perhaps it could also be used to locate people in a fire, although you'd face the calibration problem I mentioned above.
I think the accuracy would be too poor, for that. However, years ago, I recall seeing similar research about using mm-wave for body tracking in VR. That seemed more promising.in relation to gaming/media would be a good, cheap way for VR body tracking and motion capturing.