I have a switch under the dash that Im not quite sure what it does. I have an 07 XLT supercrew. Has the factory alarm I imagine. My brother has the same year, but no switch. Doesn't seem to do anything, tried to trace wires, the seem to join up with some other wires under neath the steering console area. Thought maybe it had to do with turning off the alarm, but doesn't seem to do that.

Here'a a pic:

http://dl.dropbox.com/u/8102696/photo-1.JPG

 

Looks like someone ADDED some accessory....it's a GOK switch. (God Only Knows)