The only light I'm familiar with (I have two of them personally) that works like this is the Radbot. There's probably others, of course.

The Radbot 1000 is a great light, I think even better than it's closest competitor, the ubiquitous Planet Bike Super Flash, and I really do like the pulsing light feature. As for how effective it is, I don't know, but it does get my attention.

It's also more sturdy -- doesn't need a zip tie or tape to keep from opening up. The downside is that you need a screwdriver to change the batteries, but since you don't have to do that often I don't see it as a big deal.

Thought I did think it sort of went all the way off, at least for a bit, each cycle. Maybe I'm wrong though.