[nradov]

Rear view mirrors are already available. You can just clip one to your helmet or handlebars.

[rhinoceraptor]

Yes, but serious cyclists are into the fashion and aesthetic of looking 'pro'. There are a million little details, and a mirror is a big faux pas.

[dylan604]

That's their problem. If you're doing something for the look, then maybe you should reconsider the why.

[schwartzworld]

https://www.amazon.com/Rearview-Spy-Glasses-Mirror-Vision/dp... Here you go