I would like uninterrupted power. I was looking at this at Adafruit.com

USB Battery Pack for Raspberry Pi - 10000mAh - 2 x 5V outputs : Adafruit Industries, Unique & fun DIY electronics and kits

The charging circuit will draw 1A from a 5V supply (plug a microUSB connector into the pack and then to a computer or wall adapter). You can charge and power something at the same time but the output switches to the USB input when charging so the output voltage may fluctuate. Its not good as a 'UPS' power supply for an embedded linux board, although microcontrollers like Arduino may not care about the voltage drop as much. Also, there's ~80% efficiency loss on both ends so if you charge it at 1A and draw 1A at the same time, the battery pack will eventually go empty. However, if you're powering something thats 500mA or less, you can keep it topped up no problem.…