One of the problems with the just need a key fob cars is if you place the key on top of the car. The car can start, you drive off, key falls off of car, and you get to your destination turn off the car and it will not re-start because you don't have a key fob. Don't know if it works on all cars with the fob only start but i have heard of it happening.

Do know that if you place the key fob in the trunk of a Corvette the receiver will not see the fob and when you close the car everything locks and you will be calling onstar to unlock the car. And no i didn't do this one, i was out with a friend of mine in her new Corvette and she locked us out of the car.