This is an interesting summary. And I do think that an intelligent and wider use of sensors will eventually become the killer app for wearables, because everyone wants to be healthy.
I did specifically mention the Apple Watch, because it is known that the company has hired people with PHDs on various non-invasive sensors like blood oxygen, but also and importantly, blood sugar, and more. I looked up this tech, and it seems it is not ready for prime time, you'd want it to work out of the box and for everyone no matter what kind of skin you have (not only race, but also how dry). And then there is the challenge of passing regulations, because anything more than a heartbeat sensor requires certification. These certifications take a long time, and in the case of Apple, they wouldn't want to wait 3-5 years to release an Apple Watch with updated sensors, hence if my intuition is right they could be working on sensors in a bracelet which can be certified separately, and which could communicate with the watch using the little port near the lugs.
Anyway, whatever brand will release a comprehensive health monitoring wearable at a good price may well have a product hit on its hands on the level of an iPhone. Hence the interest of Apple and others in this domain. I find this category of health monitoring devices very interesting since they could truly improve life quality in various ways, detecting disease earlier, tracking diets, etc That is progress to me.
Of course this being slashdot, many will point out the risk on privacy leaks - like imagine an insurance company gtting hold of your wearable stats. Yes, proper data privacy will be a crucial element in the design of these devices.
These are interesting times, I think we will see such an upgraded smartwatch (perhaps by Apple, perhaps a clever startup) in the next 5 years, and I think it will be huge.