I'm surprised people are still asking this type of question with dynamo hubs having been out for a number of years now, so perhaps their marketing needs improvement.

I use a Son28 dynamo hub which though initially a bit pricy, comes with a 5 year warranty.

With this I have an E-werk with cache battery.

The combo allows me to keep my Garmin Edge 800 gps and my iPhone charged up.

Theres lots of info out there on the topic.

Perhaps this link might help and be a decent start researching the topic OP.
Lighting systems

Hope this helps

On a side note, for me, there is nothing worse than sitting in a campground bathroom or laundry for hours at a time awaiting your phone or gps to charge, too terrified to leave it unattended for a moment knowing it will likely disappear before you return.

For me this makes the expense of my investment well worth it alone.

Solar might work for some but I dont think the technology is there yet for cycle tourists who ride during the daylight hours.
Or at least it doesnt suit me.

I've even bought a second dynamo hub to sit in my single wheel trailer
(http://www.extrawheel.com/en/3/bicycle_trailer/)
to power my notebook and Petzl Tikka2 XP headlight torch with usb rechargeable Core battery.
http://www.outdoorgearlab.com/Headla...tzl-Tikka-XP-2