Just bought myself one of
these. It's a small rechargable battery pack and is perfect when you want to use the iPhone (or iPod) on long journeys.
And, it's small enough that it fits in a pocket easily.
---------- Post added at 17:27 ---------- Previous post was at 17:20 ----------
Oh, and a hacker who tried to extort money out of some Jailbroken iPhone owners has published details of how to close the backdoor he used...
http://www.theregister.co.uk/2009/11/03/iphone_hack/
Basically, you need to change the device's root password..