Through sonar monitoring the app can track those vital signs from a 3-foot distance, sort of like a personal attendant that can call emergency services.

Our proof-of-concept contactless system converts the phone into a short-range active sonar using frequency shifts to identify respiratory depression, apnea, and gross motor movements associated with acute opioid toxicity. We develop algorithms and perform testing in two environments: (i) an approved supervised injection facility (SIF), where people self-inject illicit opioids, and (ii) the operating room (OR)

The team behind the smartphone app say opioid users who inject drugs alone have no way to ask for help if they experience an overdose but the app Second Chance® can monitor breathing and even body movement.