Thanks for the comments and noting they've now posted details.
So, that means $309 for Apple Series 5 refurb or $399 for brand new Apple 6 if one wants ECG.
Does the Apple Watch 3 detect Afib?
(Ah! Apple auto-correct first changed that to “A fib”... That could be a good feature for parents, middle school teachers, and the press corps. If the press were equipped with Apple watches that could detect “A fib”, they'd be going off all the time when interviewing or asking questions of politicians, especially one of them!)
Finally, does one have to waive privacy rights to use those features? In other words, agreeing to submit data to an Apple server or be a part of one of its health studies?