The Nomad ChargeKey is a USB-to-Lightning charger for Apple devices. It's just like your standard white charging cable, except it's designed to be carried around on a keychain. When your phone needs a charge, just stick it into anything with a USB slot — a wall plug or a computer, for instance.
At $25, it's a bit pricier than I'd like but it totally delivers on its promise, as it's convenient and completely out of sight and mind until you need it. Startups don't need to solve world-shaking problems to prove useful. Sometimes all they have to do is give people an easy way to charge their iPhones.
I've been using mine for a couple months and it's great! Here's what it looks like on a keychain: