Many cars are now outfitted with "smart" sensors that help them park, or warn of objects below eye level, etc. I was wondering if anyone knows of a rear mounted radar/sensor for a bike that would warn of a quickly approaching car on collision trajectory. I'm not a fan of mirrors (and feel I can't judge a car's side-to-side position very well with them) but think it would be great to have a sensor that would warn me of a car approaching directly behind (and on a trajectory to hit me), rather than one that will just pass me.
A quick web search turned up nothing. Does anyone know of such a product?