This kind of tech has been floating around the research world of smart home tech for over a decade now. Various forms of EM deflection and field deviation modeling have been used to be headcount sensors, gesture sensors, and body position modeling. Yup, it’s out there. Normally, it takes multiple antennas in particular positions to work, so it’s still a more controlled space kind of thing than the whole world. That said, it’s possible to do, so head’s up, we’re in for a rough ride going forward on the privacy and monitoring fronts.