I use a SON 28 dynamo on my Surly Long Haul Trucker and it was used on for example my Chasing the Dirt tour to keep my Garmin Edge 800, my mobile phone and my iPad 2 charged up. I used it conjunction with a PedalPower+ Super-i-Cable. On my Giant XTC 2 mountain bike I use a Shimano Deore XT DH-T785 dynamo hub to do the same thing.

Oh I have a SP PD-8 waiting to be built into a wheel to power-up my LoGo P-38 recumbent bike. It will do the same thing as the other dynamos.

Andrew