Perhaps the most useful service provided by Apple Watch is to provide some of us (humble self very much included) the motivation to prick yet another rosy balloon. There persist in being folks who assert that the Watch is just a better battery away from being the awesome device worn by cartoon cop Dick Tracy. It's such silliness. Please read Gordon's book. Technological progress isn't a matter of human imagination, pulling rabbits out of our collective hat (brain) deus ex machina, but rather figuring out how Mother Nature has put the world together. The earth, and all the resources in it, is finite. There's a lot less of them than 1800. Get over it.
We've arrived at the lithium-ion battery, and that's as far as we're going to get. At least for a watch form factor. Lithium is the smallest atom capable of supplying electrons, without the potential of blowing up (mostly, lithium batteries don't :) ). Until a neo-Edison invents a new atom, that is. For those wishing for more authority, MIT has a new piece on the problem. It fails to make the point that the periodic table has been fully populated, modulo accelerator generated nanosecond monster atoms, and thus the wall has been hit. Lithium is it. The hydrogen fuel cell has been around for a bit, but de-scaling down to laptop/phone/watch size is fantasy. To answer those banking on yet smaller chip nodes to make Dick Tracy's wrist thingee reality, I'll offer the following (admitting I'm not EE): at some node, Xnm (my guess for X is 10), control of, and compensation for, leakage and capacitance will drain more power than the Xnm node will save over X+nm. You read it here first.
It's really fun living in a time, the 19th century for example, when you know that you've only scratched the surface of that big ball of reality that is Mother Nature. Anything imaginable looks possible. Not so much when the periodic table is all there to see, thermodynamics have been codified, the Bohr atom described, and so on. Now we have productive corporations, even Apple, segueing to "services" to make moolah, because they see the end of growth from novel widgets.
We live in a Rand New World, battling with a Christ New World. In the Old World, recently ended, economic growth was driven by population growth with each new kid becoming a consumer, if only the necessities. The expansion of white folks into land lived on by others for thousands of years was a manifestation of that. Since contemporary Western economies no longer deal in necessities, population growth can't drive economic growth. We imported folks to do the heavy lifting, starting with black folks, but also Chinese and lower level European ethnics (from the WASP point of view, of course) all in service to the betterment of the few. With the industrial revolution came the problem of consuming output. In the Dark Age, when production was sorta, kinda one man makes one widget (and the widget went to the manor's Lord), that problem didn't exist. But with automated production, i.e. non-linear increase in productivity, the problem became manifest. If you invent a new automated, capital intensive, way to make widgets, how do you find consumers to soak up the deluge of widgets? The manor's Lord, and even including his spawn, won't be enough. In the last few decades, it's been an all consuming problem. Yes, that's a pun with a healthy dose of irony.
So, we have to figure out how to grow an economy with a relatively (with respect to recent history and living memory) fixed technology. If you look at FRED data, you'll see that USofA "output" has been increasingly non-widgets, not stuff, but "services". Unless the path down the road of income and wealth concentration is reversed, we'll be in a permanent Dark Age. The key to avoiding that is to solve the 1%'s refusal to admit that their wealth is mostly luck, so they shouldn't be allowed to keep it all. In order for an economy to grow, aggregate demand has to grow. The "recovery" from the Great Recession is the poster child for faux recovery. It's been driven by monetary manipulation, not demand growth. That 4.9% unemployment rate just reported is mostly the result of the denominator (the size of the labor force) shrinking. Consider that for a moment. The data increasingly confirm that most folks are still worse off than they were before the Great Recession. Hyper capitalism only works if the 99% consume the output, rather than just the 1%. They will only buy so many Ferraris. The Donald tries to hammer on that exposed nerve of angry white folks, but nothing in his history indicates that he would actually do anything good (increase aggregate demand) for the 99%. Certainly, his tax proposals are pure 1% welfare.
So, in the end, the Quixotic Quest for the ultimate battery is fantasy, propelled by dreams of 19th century invention. "We did it back then when we didn't know anything, so it should be easy now when we know so much more." Dirty Harry famously said, "A man's got to know his limitations". So does a nation. So do all nations. There are only so many elements in the periodic table (and a fixed supply of them here on the Blue Marble, and, no, mining them on other planets won't happen with chemical rockets), and they can be assembled into only so many molecules (far more on the organic side, but still true). Thermodynamics proves that there's no such thing as a free lunch. And so on. The great discoveries of the 19th and 20th centuries have brought us to the walls of this box we call reality, and the structure of our society and economy will either adapt to this very different reality, or we'll end up like the rats in the experiment. We can have continuing, robust, economic growth (with or without a battery an order of magnitude more potent than lithium-ion) without burgeoning population where just 1% skim off the production. We just need to spread the wealth around. It will be spent on fancy services that all can use happily. Ayn or Jesus? Take your pick.