Also, you get louder sound and basically a free iPod dock without the charger. Although, it does save a lot of battery. I have a 2GB Gen1 Nano, which, when it has that last sliver of battery, usually lasts about 2 minutes. This little idea stretched out that last sliver to an hour. Basically, it gave me a 3000 percent boost, and cost nothing. I have no idea how it works with other iPods or if my results were even correct but I'm sure it will at least get you a noticeable battery life extension.
It works off the concept of the iPod having to supply electricity to the earphones you use. When you use a method of sound transport that is separately powered, the iPod doesn't have to supply it power.
Step 1: Obtain Your Speakers.
Step 2: IPod, of Course.
Step 3: Connections Are for the Win.
And for those who say, "Just use your ipod wall charger." that also defeats the purpose of this instructable. This is for when, say, you don't have your iPod to USB connector or something.
Step 4: Turn It Up and Enjoy.
Sure, it's a simple and fast solution but I found it really helpful for my own purposes.