On my single light tourer / all-road bik, I have a dynamo hub plus USB converter that I use to charge my Garmin 800, and some other devices. The USB adaptor is called The Plug and is sold branded as Tout Terrain or Supernova. The assembly goes inside the steering column, and the plug is located at the top cap, so it's a very sleek-looking option. It will fit in most steering columns, but not ones that have super-thick carbon walls. When travelling above 15 kph, it provides a good charging current to the Garmin. When plugging it in during a high-speed descent, there is a lot more power and the Garmin gets a lot of juice. The Garmin 800 will last for 10-12 hours by itself, but it's nice to have this for those extra long rides.

I also have dynamo lights, previously the B&M IQ Cyo, but I recently upgraded to the Supernova E3, which has a much wider beam pattern which I prefer, it's especially useful on twisty descents. You can even run both the light and charger at the same time, although the light's power is slightly diminished, and you need to maintain a decent speed.

When we go on a long tour later in the year, I'll be transferring the dynamo, lights, and charger to our tandem. The Garmin 800 picks up the chainstay-mounted ANT+ sensor without any problem on the tandem, and my wife's Garmin 500 does the same.