12 volt only when armed (2016 Silverado 1500)

[WiseSkys]

Looking for a way to power my dash cam while parked (only while armed).  I’ve hardwired the camera/microSD-DVR to the “ignition on” source and it starts recording on each trip, but I would like to add the ability to record continuously  if I arm the alarm system.  I plan to isolate the sources with 12v diodes to prevent feedback to the alarm system, however I’ve looked through schematics and haven’t found any info on the alarm circuit.  Wire color and location would be great, but I’d settle on any reference point or even a ground-while-armed trigger would do the trick.