What is this thing? :)

Ok I recently "inherited" a 1 owner 02 Frontier - 4 cyl auto... It needed a LOT of work, most of the front end suspension needed replaced, column mount gear selector sticks in park most of the time, and some other things... I found this "switch" dangling beside the parking brake foot pedal. Original owner has no idea what it is, never had any aftermarket things installed... I pulled it up from where it was and screw mounted it to the dash so i could more easily see differences with it on and with it off, and other than the little light at the bottom of it coming on when pushed and going off when pushed again I see it doing nothing "visible". It only works when the ignition key is in the acc or on position... any ideas?