If you live in NY (not in the sticks), you would appreciate this "safety" gadget. Here , we have young guns flying up our asses at 90+ miles per hour, changing lanes at warp speed. I for one appreciate seeing the flash up ahead , at height, so I can start slowing down before the guy in front of me slams his brakes. My Challenger has it and I know it has saved me from many rear end collisions. I for one do not need the headache of losing my new ride to an a-hole riding into my ass. The ones I see on the rice burners, have them so low , that only the car immediately behind is the only one to see it. My Challenger flasher only flashes 3x and then remains steady. If you start and stop in traffic, it will not continually flash. You need to drive for at least 15 seconds before it will flash again. So, if you see one that repeatedly flashes at every brake tap, they went the cheap route. Its supposed be an "attention getter" and they work.
Many of the thousands of accident reports that I took over 28 years......#1 answer : I didn't see them.