Tomorrow (we suppose) the Apple Watch will be out. For months, there’s been lots of interesting documentation on Apple’s site — but it’s all about WatchKit, the framework used on the iPhone side to run “Watch” apps. Almost nothing about the Watch itself. I think most of my previous speculations were confirmed: specifically, the part about the Watch mostly being a remote display for the iPhone:

Perhaps… just a sequence of drawing orders? The important part is that there’ll be a single process on the Watch for doing the UI, and all the application-specific parts can be offloaded to the iPhone.

So, for now, the application logic will all be on the iPhone side — where the actual WatchKit part runs — and “assets”, meaning storyboards, xib files, and PNGs with pre-rendered icons, buttons and so forth, are downloaded to the Watch and displayed as needed. My back-of-the-napkins calculations about battery life (around 15 hours) still seem valid: Tim Cook said that you’d have to charge the Watch every night. I also said:

Watch OS … will not be a stripped-down iOS; maybe even not a Darwin derivative. It will be a highly optimized embedded system that runs as few processes as possible. It will be very robust because it will be able to do only a fixed set of functions.

Of course, this clashes with everybody else’s assumption that of course the Watch will be running iOS. Apple continues to be very careful about this: the OS that actually runs on the Watch is named nowhere that I could find. Likewise no hardware specs beyond the two screen’s pixel sizes were revealed. Details about the OS may not be revealed until next year, when developer apps supposedly may run on the device itself. It might make make sense for Apple to repurpose, say, the OS running on the smaller no-app iPods.

Beyond speculations about functionality, rumors have concentrated on price and updatability. I’m not competent to speculate about prices, but John Gruber’s final thoughts on the issue seem very reasonable.

Opinions are split on updatability, since few of Apple’s products can be upgraded, and none can have their hardware updated to a next generation. Then again, here’s a completely new type of product, smaller and (in some versions) more expensive than any other; it’s also, perhaps, the most personal Apple product ever. If you get an expensive Watch, say, as a graduation present — with an engraving, perhaps — you’ll be very reluctant to dispose of it and get a new one in a few years, even if the new version does much more.

At absolute minimum, the battery will have to be replaceable, and in my opinion, the entire Watch module (probably including the battery, probably excluding the display) will be upgradeable for a fee once a better version comes out — maybe not forever, but for at least 2 or 3 generations. We’ll see.