I recently installed a third brake light flasher after reading about a programmable model that had accelerometers and all sorts of fancy settings.
Vehicle Brake Light Flasher Module with brake force monitor Vehicle Brake Light Flasher Module with Brake Force Trigger. [FLSHR_G1] - $29.95 : 3rd Brake Flasher Web Site
you can change just about everything...
initial flash count and speed,
medium braking flash count and speed,
heavy braking flash count and speed,
lockout time,
etc.
i did the initial programming on my bench, it took some time to wrap my head around the menu structure, and i wired a momentary switch to the programming wires to make it easier, but once i had it set the way i wanted it it was time to install.
the kit comes with crimp on bullet connectors and wire taps. in the sedan you remove the 5 locking pins in the top of the trunk liner and pull down to access the wires.
you snip the positive wire, crimp on the connectors, and then tap into the ground wire and thats pretty much it. i used 2sided foam tape to mount the unit in the correct orientation so the accelerometers work properly.
some initial setup issues were worked out quickly and i absolutely love the product now.
it kinda grabs your attention and says "HEY! IM BRAKING!" in a cool, yes-its-modified kinda way.
heres some vids
https://goo.gl/photos/E6FDCFZxqSNyrone6
https://goo.gl/photos/kRNgadvZoYbpJ4qA9