I assume You want your cell phone to call a number by the car's alarm.
What phone/service/country ?
Dose your Phone Have a " speed dial " key?
Here in the US the FCC requires that all cell phone company's give "911" access even on deactavated ones! Newer cells have a "GPS" chip.
If You can program a speed dial key, Hack the keypad, are make a box and use a solonoide to push the button!