This is based on a recently discovered patent that was awarded to Apple, in which the filing of the patent is for “earbuds configured with one or more biometric sensors. At least one of the biometric sensors is configured to be pressed up against a portion of the tragus for making biometric measurements.”
Note that this isn’t the first time that we’ve seen Apple explore the idea of using headphones as a fitness tracker, but the fact that we’re seeing another patent does suggest that Apple’s interest in it might be more than passing. However should Apple ever release such a device, they wouldn’t be the first to do so.
Companies such as Jabra and Dash have launched earbuds that do come with health tracking capabilities, where it can measure things like heart rate, VO2 Max, and more. However whether or not Apple will actually go through with this and turn it into an actual product remains to be seen, as is typically the case when it comes to patents.