From the makers of the companion bicycle seat (thebikeseat.com) comes Velo+Alert=Velalert. http://www.velalert.com Alerts you of oncoming cars behind you in your blind spot so you can react before it's too late! Website says it's in user testing (how can I become a tester?) seems pretty cool. Wonder about cost. I've used Lidar devices on ships and they are VERY expensive.