I've just seen this. Apologies if done before.
A great idea but looks a bit clunky and vulnerable. I can carry a couple of power banks to keep a phone charged for about 4 days of wild camping. I wonder how effective it is at generating power.
They can run buses on motions now;
[img] 
[/img]
It's a bit difficult to see facts on how much you can generate, which is surely the whole point of the thing!
As you say, it's also the size and weight of a decent piggyback battery, which could keep you going for a couple of days anyway.
I guess if you put it on your leg while pedalling (or on the swingarm offroad), it might be enough to keep a phone going indefinitely, which I can see having it's uses.
I'm pretty sure most of these will get charged at the wall, then used like a battery and then charged at the wall again.
With it being wrist mounted some peopple on here will be hoping that it has overcurrent cutoff on it.
Very similar to [url= http://www.notpauciloquent.net/2015/02/27/pornhub-generates-electricity-through-the-****band/ ]this[/url]