Thanks to those who weighed in on this thread, I have been using the Magene radar taillight with a Magene head unit. I find it a nice feature to have. It definitely detects vehicles a bit sooner than my ears can. I've had a couple of false negatives where the vehicle behind me is moving too slowly to be detected, and found that it also fails to detect motorcycles. I'm not one to constantly look at my head unit while riding and I wish there was an audible alert instead of just a visual one (the head unit is supposed to beep when a vehicle is detected but despite playing around with the settings, mine does not beep at all). But overall I am pleased with the functionally of the radar system.