Apple Watch has proven to be a lifesaver many times over for its owners but now it’s also being used to help save people that don’t even own one.

A physician in San Diego recently shared how he used the ECG on his Apple Watch Series 4 to detect atrial fibrillation in someone while chilling at a restaurant. And it probably saved the person’s life.

Stanford scientists have declared that the Apple Watch is capable of safely identifying the heart rate irregularities known as atrial fibrillation. This is a big step in the Apple Watch being taken seriously as a medical device. A-fib is the leading cause of stroke and hospitalization in the United States,

The research was based on a virtual study involving upward of 400,000 participants. The work was funded by Apple.