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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.
https://spinoff.nasa.gov/FINDER-Finds-Its-Way-into-Rescuers-Toolkits
Microwave based ground penetrating radar is actually different from WiFi. Also the technology referenced in the link is a motion based body locator, not an identity recognition device.
This is different technology doing different things than what the original article was talking about.