Google is beginning to roll out its Loss of Pulse Detection feature to Pixel Watch 3 owners in the U.S.

Loss of Pulse Detection, the smartwatch’s marquee health feature, calls emergency services if the Pixel Watch 3 can’t pick up your heartbeat while wearing it. It was initially announced alongside the Pixel Watch 3 in August last year, and has been available for European users for months. However, because this is a high-stakes feature, it requires regulatory clearance — something Google didn’t get from the Food and Drug Administration until late February. Google says in a fact sheet that it tested the algorithm with over 100,000 hours of data to minimize false alerts, and has published a peer-reviewed study in Nature.

You’ll have to wait until you see a prompt on the watch to enable the opt-in feature. But don’t worry if you don’t see it just yet. While rollout starts today, Google spokesperson Bridget Starkey told The Verge in an email that users may see it over the next couple of weeks.