I picked up a Bike Pedaler's Take a Look mirror after seeing a review in Bicycling. The $12 mirror clips on to glasses or helmet and provides a good field of vision. It comes in regular and compact. I opted for the regular version. It's not huge by any means.
I have been commuting to work, and the streets are crazy, and I was chased a block last week by a hopefully friendly pitbull. I figured why not?
I took the mirror out for a test ride around the block and it performed well. I moved out from the glasses to the helmet, and I think I liked it there better. My only fear at this point is that I will run into something ahead when looking rearwards.
I will report back soon. I was never cool to begin with....LOL!