I know the sms works well. Mate had his custom 200sx in a carpark, got a message, left the workplace to have a look and seen two people in what they found out to be a stolen Supra trying to break into it. Problem was he yelled out, should have called a couple of mates and snuck up on them!
Still don't get why police don't invest in $5k skyline, leave it out in the open with gps system then track where it ends up. Can't be that hard.