At its September 2017 event, the tech titan announced the Apple Heart Study. The idea is to test the Watch as a replacement for traditional heart sensors—but only if it’s proven to be accurate and consistent.

The Apple Watch 3 will come with a revamped heart rate monitor, which will collect data things like post-workout recovery heart rate and abnormal spikes in heart rate while at rest. The heart rhythm tracking feature could be particularly important for patients who may not know that they suffer from cardiac arrhythmias, including those who have atrial fibrillation (AFib). At least 2.7 million Americans have the condition, which consists of an irregular heart beat that can lead to blood clots, stroke, and heart problems including heart failure, according to the American Heart Association.

The heart study is Apple’s latest foray into health care. The company’s ResearchKit service has been used by dozens of big-name drug makers and medical academic institutions for clinical research and the company may turn the iPhone into a personal medical chart. Rumors have also been swirling that Apple wants to create a glucose monitoring app that could be used by people with diabetes.

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While the company’s health care ambitions are lofty, CEO Tim Cook told Fortune in a recent interview that it’s entirely possible some of its bets in this field will never actually become money makers. Heart monitoring, however, could be an important opportunity.

“We started working on the Apple Watch several years ago. And we were focused on wellness. And wellness was about activity monitoring and also about performing some measurements of your health that people were not measuring, at least continually. Like your heart,” he told Fortune. “Very few people wore heart monitors. So when we got into working on the watch we began to realize that the things that we could do were even more profound than that.”