Boy let me tell you, that iPod with the Video really sucks up the battery!
Last week while sitting in the airport for hours (and hours) I was able to watch many videoblogs and a few of the appendixes of Lord of the Rings (thanks HandBrake!) but it could not have happened without the Griffin TuneJuice.
It takes a single 9 volt battery, but be warned, it chews through them pretty quickly. I used two within the span of a few hours. I was watching video though, I’m sure you’d get better performance froma purely audio experience.
There’s also a product from Belkin called the Battery Pack for iPod w/Dock Connector which is similar but uses AA batteries. If I thought it was something I’d use all the time I would have gotten the Belkin product, which is way more expensive, but I figure I’d make it up in batteries, since I have a bunch of rechargable AA’s.
I’ve also got a 9 volt adapter for the car, so for long car trips the TuneJuice should work quite well… Nothing keeps the kids quiet like watching The SpongeBob SquarePants Movie.