2-way your pager will beep to let you know that your car started or if your alarm is tripped. I have it on my starter but lost the pager so i'm usign a cheap generic one without that option.

double protection is so that when you get to your car and put the key in it wont let you crank if the car is on. Sounds dumb but it's like a reflex to crank when you put your key in the ignition.