Sometimes you need only a little extra power; other times, you need serious battery backup. If your needs vary, consider the Lepow Add Power Bank.
The base unit (which comes in taffeta white, raspberry pink and sky blue) starts with 4,500mAh of power; you can snap on a supplementary power pack (which only comes in concrete gray) for an additional 4,500mAh boost.
The base has a USB output port and micro USB charging port; the supplementary pack has a micro USB port. It ships at the end of March.
Price: $99.99; $39.99 for supplementary pack
Capacity: 4,500mAh; another 4,500mAh w/ supplementary pack
Dimensions / weight: Base: 4.7 x 2.4 x .4 in. / 4.23 oz. Supplementary pack: 4.4 x 2.4 x .4 in. / 4.23 oz.