Cyclist Blind Spot Haptic Feedback Device

[Ming the Merciless]

Does it vibrate both shoulders if someone is directly behind you?

 

[Boopop]

I thought at least in motoring terms, a blind spot is somewhere you can't see even after you've turned your head. By that definition, the only blindspots I have are what's obscured by my body and bicycle...I think it's a bit too late by that point!