I recently installed the Accessorides remote start (OEM with takeover) kit. Here is how it works.
1.) To remote start the car, press the lock button three times (not as fast as you can, about 3/4 second between presses). The car will start. Because you use the lock button, the doors are locked.
2.) You unlock the car (either via the fob unlock, or pressing the button on the
door handle with the fob in your possession. The takeover model keeps the car running.
3.) Enter the car with the fob in your possession, and press the brake pedal. The vehicle is fully on and drivable.
If you do any of the following, the car will shutoff.
1.) Press the lock button three times again.
2.) Unlock the car, but do not fully start it (step 3 above) within 45 seconds.
3.) Enter the car without the fob and press on the brake pedal.
The only thing I haven't figured out, and is not mentioned in their instructions, is if I remote start the car, but never unlock it, does it eventually shutoff. I tried to test this, but it did not shut off after 10 minutes in my test. I did not try for a longer time.
So, overall, I think it is pretty safe. Once you remote start the car, you need to have the fob in your possession inside the vehicle for someone to take off with it.