Hello,
It would be possible to connect to car alarm system to send sms or data if car's alarm system computer control unit is used and can deliver digital signal to any of digital inputs used by FM devices, if the signal could be sent when alarm is triggered by reading the din parameter you can set it to trigger event (either to send data or SMS, when digital input value is changed).
Towing detection would work even if the car is parked underground, this function determines car movement not by GPS coordinates, but by accelerometer used in FMB devices. The event data will be sent via GPRS connection.
Best regards.