I have a modulated brake light on my SM that I got from Brent. It flashes quickly at first and gradually slows down over a couple seconds to 'steady on' when the brakes are applied. I've been thanked a couple times by people behind me who have said it really helped get their attention that I was on my brakes. It's a simple installation and works well. I recommend it as an 'add-on' item that serves a practical purpose quite effectively.
