Apple Watch detects irregular heartbeats in U.S. study - Reuters https://www.reuters.com/article/us-apple-watch-heart-idUSKBN1XN2S2

"Apple Inc’s Heart study, the largest yet to explore the role of wearable devices in identifying potential heart problems, found the device could accurately detect atrial fibrillation, the most common type of irregular heartbeat, U.S. researchers reported on Wednesday."