I finally got around to trying out my wacky idea: a convex mirror on the handlebars that allows you to look forward without tilting your head up. The basic idea is to allow you to ride with your head down more often, avoiding neck pain. The mirror warns you if any obstacles (drain, animal, person, other rider) are coming up.
I got a small convex mirror at the auto parts store for $2, drilled some holes and attached it to the handlebars with zip ties:
It's easy to adjust so that you get a good view. In this photo the "X" is the shifter cables.
Then I took it on a 50-mile ride for testing.
The verdict: It does work as expected. I can ride on a safe road while only looking in the mirror. It doesn't take long to get used to the image being small, upside down and backwards. It feels a lot like watching a movie on an iPod. It doesn't feel unsafe, and one could ride many miles looking only in the mirror.
HOWEVER, it just doesn't feel right. I found myself looking up as often as I did with no mirror.
Also, when riding behind my wife, it makes her butt look fat.
So it was a fun experiment, but I'm taking it off the bike.