A Fox News report examines SignalTrace, a technology that links wireless device signals, such as those from phones, smartwatches or headphones, to vehicles caught by automated license plate reader (ALPR) cameras. By repeatedly matching devices that consistently travel together with a particular car, the system can build a recurring "electronic fingerprint" associated with that vehicle, which investigators can then use to trace connections when one of those signals turns up elsewhere. The report comes amid wider scrutiny of ALPR networks, whose privacy implications have drawn criticism even as operators defend their crime-fighting value.

The piece cites Flock Safety, whose CEO Garrett Langley defended the firm's license plate cameras on Fox & Friends, saying the technology helped solve more than one million crimes last year. It describes how the system works in practice: a car passes a plate reader that logs its number, time and location, while a separate sensor picks up nearby wireless signals; over repeated trips, software can identify devices that consistently accompany that vehicle, creating a pattern investigators can later use even before they know who owns a given device.