In this day and age, we should not need to use any keys or buttons. I have done away with the key remote in my car using this simple setup. I came to the same conclusion as this gentlemen in using the apple nike+ sensor to provide a proximity sensor to the car.
https://www.sparkfun.com/tutorials/135
His code lacks a couple things that I was looking for.
1) decoding of the apple serial protocol so that i can use any NRF module
2) detection of when to stop strobing the remote (when the key is inserted)
3) ability to open the trunk
and since I can detect when the key is inserted,