Interesting idea. It would be more expensive, but I like the fact that it would be a lot less bulky. Also, since it would have a pressure regulator, it could have two or three buttons, one for each level of volume you want. You want super loud for when a motor vehicle is cutting you off very close, but you don't when you're coming up behind a pedestrian. Then again, if the pedestrian has headphones on and is where he shouldn't be, he deserves a loud blast.