How Wi-Fi sensing became usable tech

Over a decade ago, Neal Patwari lay in a hospital bed, carefully timing his breathing. Around him, 20 wireless transceivers stood sentry. As Patwari’s chest rose and fell, their electromagnetic waves rippled around him. Patwari, now a professor at Washington University in St. Louis, had just demonstrated that those ripples could reveal his breathing patterns. A few years later, researchers from MIT were building a startup around the idea of using Wi-Fi signals to detect falls. They hoped to help seniors live more independently in their homes. It’s a tantalizing idea: that the same routers bringing you the internet could also detect your movements. Fast-forward nearly a decade: we have yet to see a commercially viable Wi-Fi device for tracking breathing or detecting falls. In 2022, the lighting company Sengled demonstrated a Wi-Fi lightbulb that could supposedly do both—but it still hasn’t been released. Wi-Fi sensing as a way to monitor individual health metrics has, for the most part, been eclipsed by other technologies, like ultra-wideband radar. But Wi-Fi sensing hasn’t gone away. Instead, it has quietly become available in millions of homes, supported by leading internet service providers, smart-home companies, and chip manufacturers. Soon, thanks to better algorithms and more standardized chip designs, it could be invisibly monitoring our day-to-day movements for all sorts of surprising—and sometimes alarming—purposes. Yes, it could track your breathing. The flip side of this, however, is that it could also be used for any number of more nefarious purposes.