A massive rechargeable battery pack for your Raspberry Pi (or Arduino, or Propeller, or anything else that uses 5V!). This pack is intended for providing a lot of power to an iPhone, cell phone, tablet, etc but we found it does a really good job of powering other miniature computers and micro-controllers.
Inside is a 3300mAh lithium polymer battery, a charging circuit (you charge it via the USB cable attached), and two boost converters - one that provides 1 Amp and one that provides 500mA via USB ports. The 1 Amp output is key for when you want to power the Pi since it can draw up to 700mA without anything else attached! We hooked it up to a 2.5" NTSC display (powered from the Pi's 5V breakout lines), wireless keyboard/mouse and a small WiFi dongle and it hummed along just fine as a mini computing setup!
How long it will last depends a bit on what you have connected. We ran a 'headless' pi (no keyboard, mouse, display attached) with a mini WiFi adapter plugged into the USB port and pinged it once a second to keep the network connection from going to sleep and it lasted 5.5 hours. There is a 4-step LED charge status display and an on/off button.
Comes with the battery pack, a fabric bag to store it in, a USB extension cord, a mini-B cable, a micro-B cable and an Apple 30pin cable.