Apple announced in September that its new Apple Watch Series 4 is capable of taking electrocardiogram readings as part of its health-monitoring features. That feature didn’t ship with the watch, but it’s now available to users in the US with the watchOS 5.1.2 update, along with irregular heart rhythm monitoring on all supported Apple Watch models.

The Apple Watch Series 4 promises to detect falls, identify atrial fibrillation, and let wearers take electrocardiograms on demand. Rich Mogull draws on his paramedic training to evaluate how effective each of these technologies is likely to be.

If you’re watching your weight, the Eufy BodySense helps you track it for about the same price as any other quality digital scale, but it can sync its data to your iPhone and Apple’s Health app.

Smartwatches like the Apple Watch are saving lives, but they’re not quite legitimate medical devices yet.