Energy and persistence conquer all things.
That quote is emblazoned on the side of the packaging of the 3G JUICE. It's placed there to make you think about how fantastic the product is, or to contemplate on the amazing piece of technology inside. Maybe the intention is simply to be a handy tip for life. A reminder that if you put enough energy (lol energy, it's a battery, get it?) and stick at something for long enough, that you will accomplish anything. A noble quote, totally, but if you read that quote, which, may I remind you, is written on the side of an iPhone battery box, you are a douchebag. If you don't know who Benjamin Franklin is, you're also a douchebag. If you liked that quote after reading it on the side of a box and don't know who Benjamin Franklin is, you're a velocodouche.
The 3G JUICE (in caps as that's how it's written on the blurb on the back of the box), is a rechargeable lithium polymer battery with a dock connector on it. Simple. Anything with a dock connector, the 3G JUICE can power. iPhones, iPods, iPod Touch, your mum. Wait, not the last one, she doesn't have a dock connector. Besides, she brings her own batteries.
Why does one need an extra battery for their iPod or iPhone? For the iPod, you probably want it because you're going on a long trip or plan to be somewhere where you can't charge your iPod for a while. The iPhone however, you will need if you plan on being outside for more than 3 hours. An exaggeration, but iPhone 3G owners know what I'm getting at. This is not Apple's fault or the iPhone's fault. Many things outside of Apple's control lead to poor battery life on the iPhone and hence, the need for a product like the 3G JUICE: