While we've seen USB battery packs for mobile devices before, Exogear's Exovolt plus battery pack claims to be the first that offers stackability with a "sleek modern design," as reported by Engadget. The main unit is charged via its MicroUSB port while a full-sized USB port provides power for your mobile devices. A four-LED indicator light shows how much power is left in the stack, and each battery pack (including the sub units) contains 5,200mAh of power. Exogear claims that the Exovolt Plus is "made for iPod, iPhone and iPad," and while this does show in the industrial design, the battery pack should work with any device that can charge over USB. The Exovolt Plus is still labeled "coming soon," but the main unit will sell for $89.95 while each sub unit will cost $49.95 when they make their official debut.