WASHINGTON (AP) — Too often people die of an opioid overdose because no one's around to notice they're in trouble. Now scientists are creating a smartphone app that beams sound waves to measure breathing — and summon help if it stops.

The app is still experimental. But in a novel test, the "Second Chance" app detected early signs of overdose in the critical minutes after people injected heroin or other illegal drugs, researchers reported Wednesday.

One question is whether most drug users would pull out their phone and switch on an app before shooting up. The University of Washington research t...