That would be a great idea if they actually self-leveled. They don't. Whenever I see someone with one of those, it is rocking up and down, spending most of it's time pointing somewhere other than at the traffic behind the rider. Add in the fact that it will quite often be between blinks as it passes through level, and you end up with a light that sends only a very occasional brief flash back at traffic. Whenever I come up behind someone who is using one of these, I usually don't even see it until I am very close (and have already seen the cyclist anyway).