add tilt sensor to 2010 dodge ram

I have 2010 dodge ram coming in. They want to add a sensor to the bed cover and have it trigger the factory alarm. I was thinking to use a DEI 507m digital tilt sensor. My questions are what wire going to the factory alarm can I tap into to add this extra trigger point, and if I use a 507M, what output can I use to trigger the sensor to "setup" Thanks in advance!

Factory alarms really dont have any trigger inputs other than door triggers. I would connect the blue(-) instant trigger from the 507m to the door trigger purple(-) in the drivers door harness with a diode, orange (-) GWA to the pink/white ignition, & red to +12V constant