There was a recent thread on gadget power options that examined the dynohub and solar power options and I got the general impression that the dynohub approach is heavy and still a bit hit and miss and the efficiency of solar cells isn't quite enough to make it a satisfying solution.

So IMHO the obvious solution is to simply take a spare external battery. There are now 10000mAh batteries that will charge an iPhone 8 times. This should be enough power for most tourists' applications until the next wall socket is available.

There are 3 options that I've found and I wondered if anyone has experience of these or other recommendations

http://www.hypershop.com/HyperMac-Mi...-USB-s/165.htm

http://richardsolo.com/9000mahmobilecharger.aspx

http://www.newtrent.com/Best-IPhone-...-p/imp1000.htm