Ed Dentel, 46, downloaded an ECG app, more commonly known as an EKG, onto his watch.
The new feature can show whether your heart rhythm is showing signs of AFib, a serious form of an irregular heartbeat which can lead to stroke, blood clots, or heart attacks.
Dentel said as soon as he put his watch on, the app alerted him to AFib.
"As soon as it finished it came back and said atrial fibrillation and I was like 'that's odd,' and so I figured OK it's just a glitch; tried it on my left wrist on top, AFib, left wrist on the bottom, AFib," Dentel said. "I thought OK, there might be something to this."
He went to the hospital and was immediately admitted and treated, likely saving his life.