LifeLites eLite LED kits
LifeLites’ eLite LED kits are more than ready to be incorporated into LEGO models, using wires to send power to LEDs which are nestled within tiny Technic pegs so that they won’t look unsightly in the final product. A Basic kit is available to power the lights, while the slight more expensive Advanced kit will come with 9 different modes with flash, fade and flicker being among some of the functions available. You will need a 9-volt battery box regardless of which eLite kit you want to pick up, so be prepared to fork out somewhere between $50 to $80 for a decent setup.
Source: BoingBoing Gadgets