Good idea, I'll get an air raid siren for my bike, pedestrians could all blow whistles when they move, people on scooters could all just shout "look out!" at the top of their voices wherever they go, rollerbladers could blow vuvuzelas then finally we'd all be safe.
Obnoxiously loud motorbikes.....You're just another look at me cunt >
That's the point for most motorbikelists.
Think Bike < Hear Bike, look for bike don't do stupid turn into bike.