Just a quick heads up.
I've been using one of these for a couple of years to keep my ipod/iPhone topped up while out and about.
They work off a couple of AA batteries and the base adapts for several models. Anyway, B&Q have these on offer now for £6, I think I paid about £16 originally.
I use an old iPhone 8GB to watch films on or listen to audio books and having this little gizmo in your bag or pocket means you can keep going for as long as you have a few batteries.