547
Humans can be tracked with unique 'fingerprint' based on how their bodies block Wi-Fi signals
(www.theregister.com)
This is a most excellent place for technology news and articles.
You are correct because something similar has already been used
https://spinoff.nasa.gov/FINDER-Finds-Its-Way-into-Rescuers-Toolkits
Microwaves are the same as wifi waves, these are able to detect bodies and whether the bodies are beating or not
WiFi uses a subset of the significantly wider microwave band. Ground Penetrating Radar also uses a subset of the microwave band. While there can be some overlap, the frequencies desired for GPR will very broadly based on what you are looking for, what you are looking in, and how deep you are looking for that thing. The wattage supplied can also differ.
WiFi and Microwaves in general are most definitely not the same thing and I will absolutely encourage you to not set up a 1kW 3GHz jamming antenna for your WiFi needs.
Could you use WiFi for search and rescue? Maybe for a narrow set of circumstances, but in almost all situations a dedicated GPR option will be better.
This also won't identify a victim, only revealing that one exists.