Don't jump into buying these without checking.
They may not all be compatiable with wiring IN to the Bosch system.
I'm failry sure that I've read that in Germany the lights have to be powered by a separate power source, i.e NOT wired into the main battery & this is why the light switch on Bosch bikes is deactivated by default.
The Bosch system is fitted to many bikes that don't have lights is the main reason I think. The German law saying that lights had to have a separate power source dates a bit, I think it has been changed otherwise the big name manufacturers wouldn't be wiring their lights in... Many companies have carried on with providing hub dynamos especially on trekking bikes.
To be road legal there has to be an approval marking. Supernova and b+m are German companies and they don't muck about when it comes to getting there products approved.
If you are in a night time accident and a victim says you blinded them it will be treated just as harshly as any dongle or other over powered problem.