This site shows a step-by-step mod to get your Nintendo Wiimote to flash an LED when it rumbles. Ingredients for this mod include a Triwing screwdriver, a 0603 LED, copper circuit tape, and some wire strippers. Pretty simple mod that will definitely add some bling to your game.
LED Rumble
http://blog.makezine.com/archive/2008/08/wiimote_mod_adds_leds_to.html