Emergency workers were able to identify four men who'd been trapped in Nepal's rubble—and then save them—thanks to a novel technology: advanced heartbeat detection.

The recent rescues represent the first ever real-world use of advanced sensing technology developed by NASA and the Department of Homeland Security.

Two prototype units of that system, called Finding Individuals for Disaster and Emergency Response (FINDER), were sent to Nepal in the days following the April 25 earthquake. (Read about how Nepal could be rebuild for the next earthquake.)

“For me as the developer of the technology, it was like sending a child off to college,” says Jim Lux, who manages the project at NASA’s Jet Propulsion Laboratory in California.

View Images International Urban Search and Rescue members demonstrate a prototype of the Finding Individuals for Disaster and Emergency Response (FINDER) unit in September 2013. Photograph by Bill Ingalls, NASA

About the size of a carry-on bag, a FINDER unit is powered by a lithium battery and sends out low-power microwaves. The waves can detect subtle movements, such as the slight pulsing of skin that reveals a heartbeat. The waves can penetrate up to about 30 feet (9 meters) into mounds of rubble or 20 feet (6 meters) into solid concrete.

That turned out to be enough in Nepal, where several men were trapped beneath up to ten feet of rubble for days in the hard-hit village of Chautara, north of Kathmandu. An international team of rescuers from several countries using the FINDER devices found two sets of men under two different collapsed buildings. It’s unclear exactly when the men were found or how long they were trapped.

One of the advantages of FINDER over microphones or other traditional search and rescue tools is that a person doesn’t have to be conscious to be found—the person just needs to have a pulse.

Searches in Nepal are ongoing, and Lux says that more survivors may be located. But 12 days after the quake, chances are slim. (Read about which of Nepal's historic sites fell, and which survived.)

Finding Hearts and Planets

The technology behind FINDER was first developed for sensing other planets. But two companies have begun licensing it for use in search and rescues, selling units for around $15,000.

Lux says his team is still fine tuning FINDER. They hope to add a calibration scale, so users can screen out rescue personnel that might be on the other side of a pile of rubble.

View Images About the size of a carry-on bag, a FINDER unit is powered by a lithium battery and sends out low-power microwaves. It can locate individuals buried as deep as 30 feet (9 meters) into mounds of rubble or 20 feet (6 meters) into solid concrete. Photograph by NASA, JPL-Caltech, DHS

Lux has also received a request from anti-poaching teams in southern Africa, who would like to use FINDER to count rhinos hiding in the bushes. (See pictures of animal survivors rescued in Nepal.)

“We need to go to a zoo and make some measurements of rhino heartbeats,” he says.