The Zzing is a USB charger for hub generators.
It contains 5 AA batteries and can be connected to your bike's hub and to any USB device which needs power. By default the current model only supplies 100mA, but forcing 500mA by software worked fine. The batteries can be pre-charged at home by connecting a power supply charging at max. 300mA. Accessories like the power supply or a bike mount which looks like the one described below are available in the Zzing Shop.
The default set (images of unpacking the Zzing) contains a bike mount for the Zzing and everything else you need. The device itself feels quite heavy which is caused by the 5 AA batteries inside. The bike mount is very stable.
Connect the cable from the bike's hub to the Zzing before you start.
Never connect the cable while biking, that may destroy the device!
When the internal batteries are charged, the blue LED on top is glowing. If you want to charge any USB device, attach it to the USB plug an turn on the switch on the bottom. You can see that it is turned on by the white LED on front. This can also be used as flashlight. It is always on as an indicator that your device is on. If you are not charging anything and do not need the light, switch it off!
When you are biking and charging at 100mA, your FR will slowly decharge. The internal batteries of the Zzing are still charged at this low current output. When you are charging at 500mA the internal batteries are decharged. You should charge the FR only up to approximately 80% because the last percents seemed to take more energy and I am not sure if there is something to avoid overcharge. There is no way to find out how much charge is left in the Zzing.
bike mount for the Freerunner
It is cheap, made of plastic only (even the parts to attach it to the bike, just the spring for opening is metal).
This bike mount is not buffered, I had it jump out of the lower part once on a very bumpy road. You could attach the lower part to the upper part with a cord as a backup solution. Luckily in my situation my Freerunner (and upper mount part) was still held by the USB cable. You will have to attach it very strong in order to avoid that the whole thing is moving around on bumpy roads!
I should also mention that the part which is actually holding your Freerunner is kind of soft (foamy?), but will keep it's shape made by the FR after some time. The spring to open the side holding parts is also working worse after a week or so.
Overall you get what you pay for and it is quite usable.
It is even waterproof if you put a transparent plastic bag with a zipper on top (which is available in stores here for deep-freezing food).