this would perhaps try to start the car by routing power to the starter, but if the car is newer than ~10 years old, it would probably have a car alarm and an immobilizer. Since the immobilizer would still be in effect there would still not be any power to the fuel pump and the ignition so the engine wouldn't start anyway, and since the car alarm would also be active it would probably go off. Bummer, eh?
And besides, if you have a stick-shift car (manual gearbox) you'd better make sure it's in NEUTRAL before placing the call (and that the parking brake is engaged).
Oh, and you'd better hang up after the first signal because otherwise the starter would engage every ~5 seconds or so. Not very nice to the engine.
I think commercial aftermarket systems are a little safer. There are car alarms with these functions built in.