separate warn away alarm

I have an 08 Jeep Wrangler with factory alarm/power doors/remote start. Several people I know with similar set ups have installed 508D motion sensors but have not connected the warn-away feature. Apparently because of a limitation of the factory alarm. I do not want to change my alarm system; I like the set up and don't want to mess with the electronics (mostly because I am ignorant and inexperienced!) But I want the warn-away chirp or beeps. Here are my thoughts, any input will be appreciated (remember I am a noob at this, so use basic language! Thanks) Can I set up a separate, basic alarm system that only receives input from the 508D first stage (warn-away) signal? All I want is a chirp if someone reaches in. Which (inexpensive) system do you recommend? And how would the basic wiring go? I would only arm the alarm (I imagine with a separate fob or switch) on occasion when I leave the top down. Thanks.

You would need a latching relay (Omron) triggered by the lock motor wire and triggered for turning off by the unlock motor wire, the 508d, a relay and a siren, or tie into your horn.