I just bought a mophie charge case that turned my slim, light iPhone into a river rock that pulls my pants down and barely fits in my back pocket (I have loose pants)! No slap at mophie, as I love their chargers (the space pack case is insanely cool)! You could say I'm looking for something a bit less bulky that doesn't heat my phone up hot enough to fry an egg (I exaggerate).
That's why I love Kickstarts like Augment— a hungry upstart offering a 1200mAh re-charge strategy that isn't likely to remove one's pants. A sturdy case that interlocks and detaches from a svelte battery which can be carried around with your loose change. Why can't someone invent inductive, kinetic iPhone charging powered by our body movements like this Seiko watch? Well, until then, Augment has you covered with up to at least a 60 percent boost to the stock iPhone charge at a size small enough to fit in your coin pocket! Get the gory details at links above. For a modest sum, you can get in on the Kickstarter pricing, even for the coming iPhone 6!