This is what I've said all along. While their are some small groups that will be interested in continual monitoring of their health, athletes, people with chronic conditions, etc., the overwhelming majority won't. Heck, most people don't even think about their health when they stop by McRats for lunch, or smoke, or talk on their cell while driving. What would make them want a device that gives them BP, glucose, etc. all day long? This is a device that would sell in tens to hundreds of thousands not tens of millions.
Do you own a bathroom scale? Or do you believe that scales are some sort of weird fancy item only of interest to a few specialized people?
How about a toothbrush? You're willing to brush your teeth everyday, or you think that's too much effort, and the cost of those brushes and toothpaste really adds up.
Look, I know there's a certain type of (rather despicable) human that loves to look down on their fellow countrymen as no better than animals (basically the Nazi view of the world) but try to have a grain of intelligence here. The number of people who truly don't give a damn about their health is a very small percentage of the population.
So the issue is not "Do I care?" (as compared to selling a device that gives you immediate updates of the price of cocoa in Cameroon, something that truly IS a specialized market). The issue is --- is the benefit worth the cost?
Since we have
(a) no idea what the benefits are. What (physically) IS an "iWatch"? What can it monitor? What else can it do (notifications from the phone, drive Syri, provide Google Now like contextual information?)
Is it sold with services (eg pay $5 a month, and you'll get report telling you if anything in your monitored stats looks worth checking out? If your pulse suddenly disappears the service will try to contact you and, if necessary, send an ambulance [basically fancier Medalert]?
(b) no idea what the cost is. The iPad came in a LOT cheaper than people expected...
(c) we know that Apple buyers tend to be wealthier, meaning that they make a different set of cost benefit tradeoffs
Everything you're saying is truly silly.
You're assuming, for example, that the value of glucose monitoring is knowing a point estimate at a single moment in time. But OF COURSE that's not the value. The value is having long term trends available so that you can see if you are pre-diabetic and if things are getting worse or better.
Similarly for sleep trends. You might sleep well today. But there is value in knowing that, over the past five years, your sleep patterns have become less healthy in the following ways, and that it might be worth trying to reverse that.