Agree, if I had an air horn that’d be a different topic. The RM are electric and make a good compromise.

Can recommend the bicycle horn sold by Riese and Müller. Elevates your game from “might get attention of a pedestrian” to “will get attention from car drivers”.

Link

Desertec failed due to geopolitical considerations (basically the Europeans didn’t want to have their next energy sourced from a region outside their control and therefore stopped funding the project)