Check out my Map Lights with Dome Light post. Powering lights in the footwells from the dome light is exactly the same concept. As a matter of fact, I intend to extend my mod to do just this come springtime. Too chilly out now. And refer to my later comment regarding the alternative way of connecting this that allows you to shut them off when desired and avoids having to remove the PITA A-pillar cover.
Be sure to heed the caution regarding replacing the dome light with a LED array. We just don't know the actual current handling capability of the dome light controller, and we don't want to find out the hard way. $$$
Note that my mod is based on the wiring in the SG (2003-2008) models. YMMV, but the approach that taps right into the dome light switch ought to be the same for all models.