Did you know your Apple Watch has a hidden diagnostic port? Yeah, well, it does and it turns out there’s a team of engineers out there currently developing a strap that could use that port to supply the watch with extra battery life. Up to 125% more, actually. It’s called the Reserve Strap and is currently at the prototype stage. It’s not known whether Apple will be happy with a third party developer using the diagnostic port; while Apple is encouraging development of straps, going so far as to provide official guidelines, they’re expecting the straps to vary the aesthetics, rather than improve core functionality. Still, there’s very little Apple could do to prevent eventual Reserve Strap customers from accessing this port, and the company plans to provide a tool to help them flip the port’s cover. More than doubling your Apple Watch’s battery life does come at a cost, since a pre-order will set you back a cool $249, with shipping in the Fall. Yup, owning Apple’s latest gadget sure is expensive.