Not sure how easy that would be. I'm actually trying to figure out how to set up my intelligent key so that when I walk up to my car it unlocks and when i walk away it locks. And also looking into making my knob a push button...
Here is what my research has found so far... This is a Nissan service manual for the pathfinder DOOR LOCKS
http://www.nicoclub.com/FSM/pathfinder/ ... er/DLK.pdf
AS for ADDING this feature
It doesn't look to be VERY easy, as you would have to install a few antennas on the 2 front doors and liftgate and change out your ignition component.
I'm sure courtesyparts has all the parts... Let us know what your findings are...
Here are also some other guides as well for other systems