Interesting, but pricey... Not to criticize, I am just used to (like during car driving) frequently make a quick glimpse into both of my bike side mirrors for incoming traffic from behind
. I think it worth approach .. I hope in addition you do have your mirrors?? But I kind of see when at certain time it may be super useful. I can imagine situation when in bright sunny day cycling along high tree that would generate quite huge shadows on the road, and having behind you irresponsible driver approaching with no day lights .. it's not that difficult not to notice it, and so then there you go!!... So idea is actually is very clever.... I'd see though vibration on my watch, not just screen display if they could do that way... pricey, but hey.. life is worth much more than $400, right?
ps: I like your 'mount'.. I'm to lazy doing that (yet for your 'radar capability' I guess it is must rather than put on side making to it obstructed in a way.. btw, I adopted my old camera bag as my bike bag... I am chip skate if something works why not, why spent.