I have a SON 28 dynamo, B&M headlight with a USB. Bought the setup with a tail light, to charge my iPhone. Depending on where you are touring, you may want to consider using a rechargeable battery pack or a solar panel. If you are touring loaded and hitting the mountains, you will not go fast enough to charge, on the uphill, and on the down hills, if they aren't very long before the next uphill, you won't get enough time to charge. That was my experience. i recently received a Cobra Jumpack 7500 mAh battery with a USB port. I will bring this from now on, as a back up. On tour, fortunately one of the guys I was riding with had a portable battery, so I used his to charge my phone when I needed the power as I was running the Cyclemeter app all the time, as well as music and an external speaker sometimes. The other battery source that I have is a lantern from Goal Zero. Again, it has a USB port for charging, and the light that it provides is fantastic. On the prairies, and most other days, charging was ok, but in the mountains, not a trusted, reliable source. For my dynamo, speed needed to be MAINTAINED at 20 km/h (12 mph) for extended periods of time to charge at best 3-4% per hour.