I've used my headlight modulator off and on, so to speak, for a few years. It DOES get people's attention, but in a dense, urban setting I sometimes feel their
random reactions to it may endanger me more. I can see both sides of the fence, the pros and cons.
I've had people in front of me pull over, too.
Maybe they think the local Police got new bikes and leathers...
A friend of mine was killed when a driver pulled out in front of him. We will never know if his hi-beam or a modulator would have helped him a bit or not--he was NOT a proponent of either. Since then, I've used it much more. If it is daylight and the modulator is not on, the hi-beam sure is.
Sometimes I worry that it annoys other motorists/riders. Other drivers do much more annoying things, so my worry never lasts too long. My option to choose.
Flashing rear lights are unquestionably a GREAT idea.