Google-owned Fitbit has submitted data to the US Food and Drug Administration to review a new passive heart rate monitoring feature for its wearable devices.

Currently, Fitbit can only periodically check for irregular heart rhythm; Fitbit users must decide to check it. Fitbit's new feature, however, could run in the background and notify people if they’re exhibiting symptoms of atrial fibrillation. This would help Fitbit better compete with the Apple Watch's EKG feature, which also checks heart rhythms and alerts users of irregularities.

In 2020, Fitbit began testing passive heart rhythm technology with nearly half a million Fitbit users participating in a study. According to data sent to the American Heart Association in 2021, Fitbit noticed about 5,000 of those participants had irregular heart rhythms. Of that group, 1,000 set up a telehealth consultation for an EKG patch. (A third later had a confirmed diagnosis.)

The results are promising, but it's still unclear when Fitbit will actually offer a passive heart rate monitoring feature on its devices. The fact that the FDA is reviewing it is a good sign, but there are a lot of unknowns.

Fitbit's Sense Smartwatch was approved by the FDA in 2020 for its ability to assess AFib using built-in electrocardiogram technology, but again, that method requires active input from the user.