Make it a keypad to unlock the door and have a key inside to start the car. Rental company texts or emails you the code that will either work immediately or at

Make it a keypad to unlock the door and have a key inside to start the car. Rental company texts or emails you the code that will either work immediately or at a certain time in the future. This would require you to have internet or cell service at some point prior to the rental (not unreasonable). The code would be good for the entire time you have the rental in case you lock the key in the car. The car would only need internet at the beginning of the rental to get the new door code and the expiration date of the rental and could run unencumbered from then on. You could take this one step further and have the code be what starts the car too.