Apple and Stanford University are studying whether the apple watch can help catch heart issues before they kill.
More than 400-thousand people are enrolled in the study. The goal is to see if the apple watch can catch irregular heartbeats ... or "atrial fibrillation."
The apple watch uses its "optical sensor," which sends a notification if it detects the person's pulse is off.
The study will be done early next year. It could be big news -- because people with atrial fibrillation don't always show symptoms.