A quick one. Does anyone know of any accessory that can be used with a macbook battery (or any laptop battery) to enable it to charge USB devices such as the iPhone? It seems silly that I've got a 5500mAH battery sat at home that for the sake of a £1 eBay adapter could provide my devices with charge for a week. If it doesn't exist I've got one word - Kickstarter! Thanks in advance for any thoughts or responses.