Search and Rescue Drone uses Phones

Makes sense, and a way to coordinate the search for multiple kinds of search conditions and requirements.

Search-and-Rescue Drone Locates Victims by Homing in on Their Phones  By IEEE Spectrum,  February 24, 2021

The Search-And-Rescue DrOne (SARDO) platform was developed to enable a single drone to act as a moving cellular base station, do large sweeps over disaster areas, and locate survivors of disasters using signals from their phones.

The Search-And-Rescue DrOne (SARDO) platform developed by researchers at Germany's NEC Laboratories Europe uses off-the-shelf components, integrating aerial drones, artificial intelligence, and smartphones to find survivors of disasters using signals from their phones.  SARDO utilizes a drone as a mobile cellular base station that sweeps disaster areas and conducts time-of-flight measurements, while a machine learning (ML) algorithm surveys the area and calculates the location of victims.

A second ML algorithm helps locate survivors on the move by estimating each person's trajectory.

In field experiments, the drone could localize missing people to within a few tens of meters in roughly three minutes per victim.

From IEEE Spectrum