It's factory. It controls a standard duplex outlet in the converter compartment. It is "half-hot", in that the switch controls one of the two outlets. We just had to move the converter plug to the outlet that was switched, and Voila!
It also helps that the converter compartment is right at the head of the bed. I think this is a great feature. I have heard of other years and models having the switch, but it is by no means universal.
Phil in Irvine
WBCCI # 9759
2002 34 Slide Out Lounge
2005 Yukon XL, 3/4 ton, 4WD, 8.1 engine