Ordinary WiFi can "see" through walls/corners with biometric fingerprinting of humans, https://gizmodo.com/researchers-issue-warning-about-tech-tha...

  Researchers collected WiFi signal recordings from nearly 200 participants as they walked through a WiFi field using different walking styles. The data was recorded from four different perspectives using both the BFI method and an older WiFi sensing approach relying on channel state information, or CSI. 

  “This technology turns every router into a potential means for surveillance,” said co-author Julian Todt in the press release. “If you regularly pass by a café that operates a WiFi network, you could be identified there without noticing it and be recognized later – for example by public authorities or companies.”

  The researchers are urging the IEEE, the organization that sets industry standards, to include stronger privacy safeguards in the upcoming 802.11bf standard, which is meant to standardize WiFi sensing applications.