This tiny little thing lets you use pedal power (along with a dynamo hub) to charge your smart device or external battery pack. Its weatherproof USB charging port sits in place of your headset cap and is wired to your dynamo hub.
The American-made Reactor is a challenger to the better-known The Plug III and is technically superior in at least two big ways: first, it begins charging at under 4 mph vs about 7 for The Plug; and second, it lets you charge a device even while the dynamo powers your lights, something The Plug doesn't do, at least without a hack.
All the electronics are encased in resin, so the Reactor is not only weatherproof but also shock resistant.
Our customers have been using the Reactor for a couple of years now, and we've had no complaints.