The Reserve Strap for the Apple Watch allowed Apple Watch users to extend their battery life to as long as 7 days, a welcome accessory when you consider that the Apple Watch itself only gets 18 hours of battery life (and 5 hours of on-screen time) on a single charge. These stats pale in comparison to what the Reserve Strap could accomplish, but the new band's accomplishments or potential mean little now, thanks to a new Apple WatchOS update.
The WatchOS update to version 2.0.1 has disabled the Apple External Accessory Protocol, causing the functionality of the Reserve Strap to no longer work as it had before. The company behind Reserve says that this is a bug in 2.0.1, but it appears as though Apple disabled smartband functionality due to its own plans to sell something akin to a "SmartBand" to its own Apple Watch users. Here's what Reserve had to say:
Beginning with watchOS 2.0.1 an unexpected change to the Apple External Accessory Protocol disabled the functionality of Reserve Strap. Until this change, Reserve Strap functioned perfectly -- extending the battery life of Apple Watch by over 150% in many cases allowing users to keep their Watch charged for up to a week.
Specifically, this bug interferes with the communication between accessories and Apple Watch. For the time being, Apple has suspended use of this port until they unveil an official MFi program for Watch. In keeping with their wishes we will also be suspending shipment of all orders until Apple supports development of smart bands.
In other words, this supposed "bug" is intentional, from Apple, and designed to prevent smartband manufacturers from selling to Apple's customers. The company apparently has plans of its own in a similar direction and doesn't want to lose this money to third-party manufacturers like Reserve. In any case, Apple has requested that manufacturers cease making smartbands until it's ready to launch one.
We could see a smartband arrive for the Watch 2 this Fall, considering that Apple has already filed a patent for smart modular bands. At this time, however, we have no proof that Apple does have a smartband planned, though this could be what the FaceTime camera refresh rumor was all about.