The Reserve Strap for the Apple Watch adds 30 hours to its current 18-hour battery life, giving you a combined charge of two whole days life. The only major drawback of this strap is it's whopping price tag of $250 (£160).
You could in fact argue that with the cost of this strap you might be better of buying a new watch, but there are several features, which actually make this strap worth buying.
The watch charges via micro USB and when you charge it, it actually charges the Apple Watch at the same time. That's great, as it means you won't need to carry Apple's official magnetic charger around -- and you can make use of the much more common micro USB cables.
The strap is made from a specialised thermoset elastomer silicone and the official battery boost is quoted at 167%. There's even an LED indicator onboard to show you how much charge you've got left.
Watchstraps of this calibre are becoming more common. Similar to the Reserve Strap, the MyCell Link Bracelet Band will set you back a similar price at $224.99 on Amazon, and its only purpose being to make you look suave.
With the Apple Watch already setting you back £299, your going to need a hefty bank balance if you kit out your watch with the best gear.
The Reserve Strap ships on November 3, if you constantly find you Watch running low on juice around midday; this gadget is the one for you.