The Sinewave Reactor is an ingenious device used to power USB devices from a bicycle dynamo. It starts charging at 5.5km/h, reaching full charging rate at 14.4km/h. It will deliver at most 1 Amp of current at 6V.
The Reactor hides the device inside the steerer tube of your bike, underneath the stem. All that's visible is a tiny cap with a USB port. It's compatible wtih 1" and 1 1/8" threadless systems.
It's totally waterproof, and the USB connector is gold plated. That means you can ride without worrying about the weather.
You can easily wire it in parallel with your light, or wire it separately and plug in whichever you need at the time.
Designed and made in the USA.