Interesting product. I, too, would be concerned about the additional weight on the helmet. I wonder why it wouldn't /couldn't be attached to your jacket (below the neck and above the shoulder blades)?
I'd also be concerned about a driver "fixating" on the light. "WOW! Look at that. Wonder what that is?" CRASH!
Given that, according to the Hurt Report, less than 3% of motorcycle crashes are rear-end collisions AND that cars/trucks have had high-mounted brake lights for several years with no real reduction in rear-end collisions, I'd probably spend my money on some retro-reflective gear (no batteries to worry about) and additional training. Position yourself with an escape route at intersections and be vigilant when riding.
Just my thoughts, YMMV.
TCARS!