I toss that idea around in my head often, cyclingYEG. I might do it as an experiment, but it's expensive, heavy, labor intensive, and not portable from bike to bike.

I might dig this thing out of retirement. The clamp is crap, so I have to fashion a different one. This isn't portable from bike to bike, either, but it's cheap. I have one in my junk bin currently.

I once had one when I lived in Boston. I remember two incidents when it worked better than I had hoped, both times in Cambridge.

In one, I had the light but the motorists had stopped streaming, and pedestrians started to flow into the street, in front of me, since they didn't hear me coming. I blew the horn, and two pedestrians JUMPED BACKWARDS onto the curb.

In the other, a car was starting to right-hook me, and I blew the horn. The motorist stopped, and I went ahead. Then when he saw that I was "just a bike" he honked back at me in anger. Well, dude, you shouldn't have cut me off.