This is a helmet I designed because I hate having people
or things catch me by surprise from behind. It appears to
be a normal, matte-black helmet with polarised faceplate.
It has flare compensation built in, but that's not the
important part. I had a tiny camera built in, with the
lense facing rearward. The images from the camera are not
recorded, but they are flashed on a small heads-up display
in the lower corner of the helmet's faceplate. Thus, I
can keep an eye on things that might be sneaking up on me
without having to turn around.
Naturally it isn't foolproof (you have to be looking
at the display--it doesn't alert you automatically), but
any advantage is worthwhile in the shadows.