The magic here is that this is baked into an otherwise useful, relatively cheap non-medical device. That device (and this test) are also entirely self-service,

The magic here is that this is baked into an otherwise useful, relatively cheap non-medical device. That device (and this test) are also entirely self-service, and the cost for both is borne by the consumer, effectively elective. Also: The heart beat monitoring features account for some portion of the Apple Watch's price, surely, but I suspect for most people this feels like a "free" benefit.