This was discussed a year ago on a thread I began:
http://www.spyderlovers.com/forums/...elp-for-additional-brake-warning-light-please!!
You might want to have a look; several possibilities were discussed - Gear Brake, Vololights, Admore and a design in development for a helmet-mounted flasher. After extensive research, during which I was advised by the manufacturers that neither Gear Brake not Vololights was really satisfactory for mounting on my F3L, I went with the Admore "Smart Brake" light which works off a decelerometer, as has been described and pictured above by george123.
The Admore system functions well and is rugged. I bought it for the same reasons you want it - I love to engine-brake and don't often tap my brake pedal. The warning light is activated when my Spyder begins to decelerate; you can use numerous different settings to have the sensitivity and sequencing that you want, including turn signals and actual foot brake signal as well. You do this by connecting to a smart phone or computer. I really only wanted to signify to followers that I was slowing up; my 2017 F3L already has turn signals, brake lights and is pretty well illuminated. I merely wanted something separate, distinct and different to convey the special message:"Hey, I'm slowing". The Admore does that; I'm happy and a lot more satisfied that I have signified to others behind me what I'm doing, because I don't often or always use my right foot. I would have placed it higher up, like george123, but didn't like attaching it to my topcase; so it got placed on the licence plate bracket, with easy access to the wiring system. Pics attached.
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