This article describes a custom creation, custom theme, or other fan material, made by a Brickipedia contributor. It has never been, is not, and will not be officially released.
The Power Functions 4 Light Set would be a cable with 4 LED Lights at the end. Two of the cable connecting the lights would be slightly longer, so they could be used, for example, in the backlights of a vehicle when the power source is near the front.
(Pictures soon, need to do some drawing!)