That's factory. It's a solar sensor for the climate control system.
It has an alarm - the horn honkin' kind - that will go off if the doors are opened without unlocking from the outside and it also has an impact sensor that can set the alarm off.
Which got me thinking, maybe if you aren't unlocking the all the doors on the car, perhaps the panic alarm you are hearing is the alarm going off because the trunk opened without unlocking.
That leads me away from the key again. You may want to consider disconnecting the electric trunk release if it persists.
Last edited by landark; 01-29-2013 at 06:50 PM..