The Apple Watch, as of Series 4 (and the current, Series 5), comes with health related features such as ECG, atrial fibrillation detection, as well as high and low heart-rate notifications. Fitbit, who recently announced it will move its production out of China, uses heart rate sensors on its trackers, however, for calorie burning purposes.
According to a Reuters report, Fitbit is partnering with Bristol-Myers Squibb-Pfizer Alliance, in order to be able to bring irregular heart rhythm detection to its wearable devices. Under the partnership, Fitbit devices will be equipped with software that could detect atrial fibrillation, pending approval from the U.S. Food and Drug Administration.
It is unknown whether the software can be updated on current devices in order for older trackers to gain functionality, or these features will be present on future devices, but we’ll let you know as soon as we hear more details.