How do you unlock a car door without the key?

You could hook up a button switch and run it into the relay for the wireless trunk release. This is found behind the kickplate on the passenger's side floorboard. Find the Green Wire with Black Stripe into the relay switch. If you place a wire into this outlet and then ground the same wire against the body metal you will hear the solenoid for the trunk release.

So, just hook up a Momentary Push button somewhere where you would like to put it in the car (one side of the connector to the relay and the other side of the connector to the metal frame [i.e. ground]).

This will create an inside release switch without having to remove the key from ignition to open the trunk.