I wired up a PWM (pulse width modulator) for my boost gauge. I got it to to regulate the light output of the LED backlighting of it. Just a cheap kit I got off ebay, but hopefully it does the trick. I'll snap a pic of it tomorrow when I have my camera and access to my server.
It was actually a lot of fun to build. I've never soldered a circuit board. I'm not good at it, but I got better as the kit progressed. I bench tested it and it works, so mission accomplished!