Originally announced by third-party developers Lane Musgrave and John Arrow back in early March, one of the biggest concerns of the battery-boosting accessory "Reserve Strap" was its use of the Apple Watch's heart rate sensor as a way to provide power to the wearable. Although it was unconfirmed, there was always a possibility of the Reserve Strap obstructing normal functions of the heart rate sensor, or causing the Watch to not function altogether by interfering with skin contact completely.

Last week, after getting their hands on an Apple Watch, Musgrave and Arrow have gone back to the drawing board on the design of the Reserve Strap, coming up with a new look that acts as more of a traditional Apple-made band without blocking the heart rate sensor at all. The new Reserve Strap aims to use the 6-pin diagnostic port - hidden inside of the band port on the bottom of the Watch - as the main source of providing power to the device, shirking the heart rate sensor's magnetic inductive charging altogether.

The Original Reserve Strap design (left) vs the new design (right)

Finally getting our hands on the Apple Watch has further confirmed the immense value of the Reserve Strap. Since release day, we've been executing series of tests on the Apple Watch and have some really exciting news to share today. We've developed and tested a completely rethought design that takes advantage of the 6-pin port underneath the band slide of the Apple Watch. This port hadn't been deciphered by anyone until now but we've been able to make significant enough observations so far to warrant shifting our development focus to this new method. We're looking forward to sharing more design details and technical specification of this new Reserve Strap as soon as we can.

The company claims in its blog posts that its engineers have "been able to independently confirm that the 6-pin diagnostic port underneath the Apple Watch case can be used for charging." They continue by also noting the diagnostic port will allow for not only a higher charge capacity, but faster, more efficient charging times. The blog post also notes that the new method should improve durability of the strap as a whole and eliminate "any interference with Apple Watch functionality including taptic feedback and heartrate sensors."