Iu used a Back-Off modulator on my past three bikes and it worked good. I bought the Run/brake kit for my H-D at 20% off and I really like that due to the extra lighting it provides with the rear directionals...
After a near rear end miss by a BMW cage two summers ago, I added one to my ultra classic. When the brake is applied, it flashes quickly 3 times before staying lit. It certainly catches the attention of anyone who is behind you.........providing they are looking straight ahead. If they are looking down and texting, nothing short of a siren will get their attention. It is a safety device and anything that can command the attention of a reasonably attentive driver is a good thing. It is also plug & Play.