I made up the "self-powered" description, but I think it's not too far off. They look really cool:

https://www.reelight.com/en/

I've ordered a set and will post some impressions on my blog (when they arrive from Europe).

Stephen

I have seen another brand using the same concept in use. The ones I saw worked very well. They don't seem to sell well where I am for some reason. There is a huge box full of them at a local discount store that buys leftover lots of things. I have not seen any on the road lately.

wonder what's more efficient, that thing or a normal continuously running dynamo hub.

Keep in mind that this will generate a force against the rider... this turns your wheel into the rotor of an electric motor. It'd be interesting to know how much faster a spinning wheel (off the ground) slows down with this attached.

But less than a standard dynamo, surely?

Just another trash.