Turns off your alarm interior sensors 
Might sound silly but how do you know if they are on or off in the first place (without activating the alarm)?
They default to 'on' when you arm the system, the pillar switch will illuminate orange when pressed to show the sensors are disabled for one cycle of the alarm and will default back to normal when you unlock / relock the car,
Iirc it also disables the tilt sensor as I use it to stop my alarm going off when the car is on a ferry due to the motion etc
