It’s pretty clear that adding an EKG would require FDA approval...
Also, as most users would not have the training to interpret their EKG there would have to be some sort of software analysis. Judging by the expensive hospital ekgs I use, software analysis is very frequently inferior or downright wrong compared to a well trained physician’s interpretation. I’m not saying software couldn’t do it, but it currently isn’t good enough. And I’m not aware of Apple running large trials to leapfrog past the current industry leaders in software based EKG analysis. Perhaps users could pay for a subscription to a remote telemetry service, although even this would result in a huge number of false positives.
Anyways, personally I’d love my Apple Watch to have an ekg (and continuous glucose monitoring). Can’t wait to see what they come up with.