you dont need to get the popper, all you would need is a pin switch to get the back door tied into the alarm, but most aftermarket alarms you get will have another chanel to allow you to open your back door, so it might be worth getting the popper kit just for convenience

on this subject.. anyone know if a glass break sensor or motion sensor can be added to our stock alarm? i wouldnt think it would be that hard... theres some sort of signal when the sensor is tripped, that wire could be tied into the one that sends the signal to the alarm when the door is opened right? like adding the pin switch from tones popper kit