Just like there are power cases for iPhones, the Reserve Strap — still in prototype — hopes to extend the battery life of the Apple Watch.

The Reserve Strap is a prototype accessory for the Apple Watch that wants to give you extra time to actively use the device. While there are no solid numbers yet on just how long the Watch's battery should last Apple has indicated that it will last about a day. The Reserve Strap uses two small batteries in conjunction with an inductive charging cradle.

From the Reserve Strap website:

These photos show our first concept--a silicon band with embedded lithium polymer cells and an inductive charging cradle between your wrist and the Apple Watch. Through prototyping, we've refined this design and come up with a few other ways to charge the Watch that we can't wait to share with you.

As previously noted, this is a prototype. What's more, there's a better than decent chance that it won't even work. Apple hasn't announced any sort of accessory plans for the Watch, and while their MFi program could be expanded to include accessories that connect to Apple Watch, there's no guarantee that this will make the cut.

Despite this, the company is taking pre-orders for the strap for $249.99, which the company says can be refunded at any time.