I tried an airzound, it was not as effective as the boat horn. Though to be fair, it was a long time ago - so long, in fact, that I could go to RadioShack and buy dust remover spray to replace the canister, and it was significantly cheaper than the official refills at marine supply stores…

I used to have one wedged between the brake and gearshift levers of my bicycle, so I could hit the button with my thumb, it was very handy.