The wonders of new (and old) technology never cease to amaze. This article from SciTechDaily posits that your own body could be used to see you based on capturing and analyzing WiFi radio signals. The tech has an incredible success rate and seems like no special firmware needs to be deployed. Who needs Ring Cameras when you have WiFi just about everywhere.
I wonder, could LTE cellular signals be used for the same purpose? What about FM Radio, or some other radio waves? I expect that LTE/5G may be the closest in density that could be used for this.