WiFi signals can measure heart rate

Everyone’s heart is different. Like the iris or fingerprint, our unique cardiac signature can be used as a way to tell us apart. It can already be done from a distance using lasers [1].

[1] https://www.technologyreview.com/2019/06/27/238884/the-penta...

https://www.theregister.com/2025/07/22/whofi_wifi_identifier... | https://news.ycombinator.com/item?id=44685869

> Researchers.. developed.. a biometric identifier for people based on the way the human body interferes with Wi-Fi signal propagation.. CSI in the context of Wi-Fi devices refers to information about the amplitude and phase of electromagnetic transmissions.. interact with the human body in a way that results in person-specific distortions.. processed by a deep neural network, the result is a unique data signature.. [for] signal-based Re-ID systems

Tracking people walking through malls. Or even better: tracking everyone in the sidewalk of a NYC street after they commit a crime and where they end up at.

Don't we have phones for that?

That only catches the stupid criminals, which to be fair is most of them.