Its too bad that mirror design hasn't been given any special attention. If it had, using them would become more mainstream and make cycling a lot safer. Since I already wear glasses, I just use a clip-on which is virtually invisible to the casual viewer.

The helmet mounted version I had before that was cumbersome and stuck out like a sore thumb. Its reflection was also quite bad since the polished surface has quite a bit of distortion. Unfortunately polished surfaces just don't work very well. Especially when the surface is that small.

Even if you don't wear prescription glasses, the eye glass clip-on is the best alternative to knowing what's behind you. They certainly are a lot more versatile -- and cheaper -- than any handle mount mirrors that I have seen so far.