We need is to know if someone is in, or moving into our blind spots without taking our eyes off the car in front of us, right?
Now check out this url: http://www.meaa-mea.com/products/b_millimeterwave.asp
OK, wild ass speculation follows ...
What if you had something like this pointing backward and then used a little GPS sized screen to display the objects it detects. You could put the screen front and center.
BETTER, if you could convert the signals to stereo audio to represent the position of the objects. Just like normal hearing. You could wirelessly pipe the sound to embedded speakers in your helmet using BlueTooth or something. I mean, when I am driving my car, that's how I know when a car moved into my blind spot. I heard it move up into position. With a helmet's wind noise and ambient sound muffling, that doesn't work without electronic help.