Kanex released its GoPower Watch earlier this week, which it claims is the "world’s first cordless portable charger for Apple Watch." It’s a 4000mAh USB battery pack with an integrated, Apple-approved Watch charger on top along with a second USB port for charging a phone.
Except of course, it’s not really the world’s first, with ZENS beating them to the market with its Apple Watch Powerbank a few months back (admittedly, with a much smaller 1300mAh battery). And even the ZENS Powerbank might have difficulty with the "world’s first" claim, give that Griffin has its Travel Power Bank that was announced back at CES (although it still hasn't shipped yet).
You probably don’t need a portable Apple Watch battery
Adding insult to injury, the Kanex GoPower Watch costs $99.95, which is almost comically expensive for what you’re getting — a good 5000mAh battery pack can be found for around $15. And for the price of the GoPower Watch, you could buy a 26800mAh battery pack, an extra Apple Watch cable to keep with it, and if the integrated cable is so important, some duct tape to tape it together, and still spend less money.
That’s assuming that any of these battery packs are necessary at all, which, in my experience, they probably aren't. I've used an Apple Watch for over a year, and of all of the issues I've had with the Watch as a product, surviving through a day of battery life isn’t really one of them. And it's certainly not one that I'd spend $50 to $100 to solve.
Correction: The Zagg Mobile Charging Station requires a separate USB Apple Watch charger. This article originally referred to it as a built-in charger.