Adding motion sensor & siren

I recently picked up a keyless entry system for my Saturn. I thought it was all I needed. Won the unit on ebay and was waiting for it to arrive. Two days before it arrived someone stole my car, couldnt get what they wanted and let is coast down a hill into a parked van. The keyless entry has an ignition kill, but now I'd kinda like a motion sensor, door open warning and siren. Is there an module I can add to my Crimestopper CS-865RKE to add these features. Like something that would activate through my negative when armed wire? Or am I stuck with this keyless entry unit and have to buy a full blown alarm as well?

You will need a full alarm. Keyless entry units don't sound with the doors and you can't add sensors.Certified Security Specialist

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