For those people who are always short on battery life throughout the day but dislike using battery cases on their device, the best option is a portable battery pack. I have a really great battery pack for review by a company called myCharge. They offer many portable battery packs in varying sizes but the one I have had a chance to use is the Portable Power Bank 6000.
This battery packs a TON of punch with 6,000mAh of power! The battery itself is very lightweight and very small for what it is. The pack has a nice, soft touch finish to the large surfaces and a brushed finish plastic band. There are a few controls that run along the band which include an On/Off switch, a charging input port, indicator lights, and button that displays the charge level and a plain USB port which you can use to plug in any device that you might have which charges via USB. What I really like about this battery pack is that there are 3 built in charging connectors. These are connected to the pack and flip out to charge your device. The 3 connectors that are built in are; a 30 pin connector for apple products such as an iPod, iPhone, etc and on the other end of the pack are a micro USB and mini USB.
Like I mentioned, this battery pack contains 6,000 mAh which gives you up to 24 more hours of talk time, 34 more hours of WiFi, 34 more hours of video and 137 hours of music! The apple connector output is 5VDC @ 2.1A and the mini/micro USB output is 5VDC @ 1A. The USB output port is 5VDC @ 1A and the input is 5VDC @ 500mA - 1.8A.
I really, really like this unit and I would recommend it to anyone. The build quality and battery power is remarkable. This unit sells for $99.99 but there are smaller batteries (3000, 2000 & 1500) also available for less than $99.99 if you don't quite need all 6,000mAh.