Signal Tracker Helps Search for Missing 84‑Year‑Old

Investigators are using a cutting‑edge device that can locate the faint radio waves emitted by medical devices such as pacemakers. The tool, dubbed a signal sniffer, was created by former NSA hacker David Kennedy.

How It Works

Nancy Guthrie, an 84‑year‑old pacemaker user, vanished from her Tucson home on February 1 after missing church. Her pacemaker sent a Bluetooth Low Energy (BLE) signal every few minutes—an energy‑saving mode that keeps devices operational for years. At 2:28 a.m., the pacemaker stopped connecting to its app, providing a clear signal‑loss event for investigators.

Kennedy tested the sniffer at home with a basic drone and inexpensive components, extending its range from the typical 10–15 feet to roughly 800 feet. With stronger antennas or higher‑flying drones, the signal could be detected from several hundred feet away.

Deployment in the Field

A helicopter flew the sniffer over the search area on Monday. The low‑altitude flight offered a broad overview of signal sources, but Kennedy believes drones would be more effective because they move faster and avoid interference from metal or concrete structures.

This technology is brand new for law‑enforcement operations, and many agencies lack sufficient drones. If 50 or more drones could patrol a large area, the search time might shrink from weeks to just days. The primary constraints remain: how many drones can be deployed and who is authorized to control them.