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.

Ah yes, tracking everyone. The one system that only leads to good outcomes.

Well, we know that tracking "everyone" would only lead to tracking a subset of everyone. A subset with a lot less money and power than those in charge of the tracking. Much like the guard or observer in the panopticon.