This is off topic, but you sound like the perfect person to ask. Do you know of a worthwhile bike rear view mirror? I have tried several varieties, on the helmet and on the bike, but none worked well.
Just put someone facing backwards on the back rack. What do you need a mirror for?
They all have their pros and cons, but in general I'd prefer the helmet mount because of the reduction in vibration. Pretty scary in a crash tho.
You need mirrors now more than we did decades ago too, because cars are so much quieter, especially a hybrid coming downhill.
TChad,
The Take A Look mirror is the best I’ve come across.
http://www.rei.com/product/752285
It clips to your sunglasses and remains extremely stable. I think you could actually read license plates of oncoming cars if you so desired.