The sensitivity of the system is your choice, every alarm system comes with a dial to adjust the sensitivity on the system, unfortunetly some people turn it on so sensitive that rain drops trigger the alarm.
Now, I would definetly recommend the pager alarms because they have the best features and they do keep you constantly in touch with your vehicle when you're in range, however if you don't want to spend the extra $200 you can always go with the basic system and add your choice of options to it.
There's many security system manufacturers in the world, the manufacturer I would recommend and never had complaints about from customers is
Directed Electronics Inc. (DEI). They have been in the business for a really long time and their quality is top notch. They also manufacure most of the bells and whistles for alarm systems.
If you are in the G.T.A. I would definetly recommend you go to
Safe & Sound Installations I actually work there but now I'm in the Middle East, I have already forwarded many Toyota Nation members and so far they have been very pleased with the service.
The shop is in Scarborough. And the contact is
Moe (416)757-7233 Make sure you mention that you are a member of ToyotaNation and that Ahmed sent you. You can ask them about their recommendations for security systems, tell them exactly what you're looking for and I'm sure they'll be glad to help.
Good luck...