What is this switch in my used 05' C320? Definitely seems like an aftermarket piece.

http://i.imgur.com/lK6So7R.gifv

The switch is located next to the exterior light controls, it lights up when switched on, I can see its wires through the drivers side fuse box, and when switched on, there's an audible click that seems to comes from the drivers side of the engine bay. I imagine that the click is from a solenoid engaging.

Any ideas on what this controls/used to control? Thanks!