I bought this in what I thought was a naive and rash purchase. Most independent cables for the iPhone 3G are either six times as much and more often than not dont work. However I was rather pleasantly surprised when I bought one of these wee devils for a quid .. plugged it into my Mac USB port ... voila.. data AND power to it. Great. Tried it with me 3pin-to-USB mains plug adaptor ... yup .. it charges ... via that .. and with me cigarette lighter adaptor-to-USB plug too!. Quite surprised really. I cannot guarantee it will work with all adaptors .. but certainly its a great and cheap way to charge and transfer data via the PC at least. And worth a shot at one British Pound, surely! Good luck!.
PS: apologies for the inaccurate piccy .. this is the best I can do .. but its in the same section as the USB Mouse and the same coloured packaging, readers!