Cars and bicycles have horns, which come in handy especially to avoid dangerous situations. Pedestrians do not have horns, and except for the occasional screaming pedestrian, they are basically silent.

A pedestrian horn would help pedestrians avoid dangerous situations. It could be worn as a necklace or watch, or even slung over a shoulder like a purse.

It would be especially useful for crossing the street in crosswalks without stoplights.