Yeah, but that directionality is bumping up against the vastly different levels of power: you don't just need a little attentuation between your target and the

Yeah, but that directionality is bumping up against the vastly different levels of power: you don't just need a little attentuation between your target and the wifi, you need something like 12 orders of magnitude attenuation. That's not so easy over long distances. See the paper OP cited which does actually do the math instead of handwaving.