All those 2 way FM/AM radio alarm does not necessary have that advertised range. Bear that in mind.
I used to sell GSM 2-way car radio alarm (uses SIM card from Maxis or Digi), which have a better coverage including basement car park. You can immobilize the car just by a phone call. Or press the panic button and it will dial to 2 preset number eg friend or relative. Imagine you park your car very far away, someone open your car door, you will be notified immediately on your phone, even if the thief remove the car battery.
Now no more stock already.