You can risk your iPhone running out of juice in the middle of nowhere, or take on the hassle of carrying battery packs and, chargers and cables. Or… you could just get the superbly compact Mophie Juice Pack. It’s small enough to dangle from your key-chain or slip into a pocket, and has its own inbuilt USB charger cable so you don’t need anything else. Just make sure the Mophie 700mAh rechargeable battery is all charged up before you set out.