My biggest fear whether riding Onewheel or euc on the street is getting hit from behind or vehicles getting too close.I've tried a helmet mirror, but found it hard to focus(too small) and hold my head steady until I can get a clear picture.
There are wrist mirrors available, but I used a larger strap on mirror meant for a bicycle and put it on my left hand ring finger, I can get a great view.I used a brand name mirror, but found the convex was too severe , I sourced a cheap offshore knockoff with less convex.The horn is a bicycle horn is good for alerting pedestrians, but no good for warding off cars. The horn has 3 tones, the circus clown tone always get a smile from pedestrians.