I added a pair of additional LED (amber) lights, for use as extra, high mounted turn signals. They work great at night, but I'm looking for something a bit more visable in the day time.
I also added a SOMA (stay off my ass) module, from Signal Dynamics, inside the trunk, that either rapidly flashes, or 'wig-wags' the brake lights. I also have one in the rear fender light.
http://www.signaldynamics.com/lighting_control.htmReally gets the attention of cagers. I actually had someone pull up along side of me and say "Did you know your brake lights flash when you stop?"

Black Dog