Unlocking car by phone

From forwarded e-mail:

For those of you who have a car that can be unlocked by that remote
button on your key ring: If you lock your keys in the car and the spare
keys are home, and you don't have "OnStar," here's your answer to the
problem!
If some one has access to the spare remote at your home, call them on
your cell phone (or borrow one from someone if the cell phone is locked
in the car too!)
Hold your (or anyone's) cell phone about a foot from your car door and
have the other person at your home press the unlock button, holding it
near the phone on their end.
Your car will unlock. Saves someone from having to drive your keys to
you. Distance is no object. You could be hundreds of miles away, and if
you can reach someone who has the other "remote" for your car, you can
unlock the doors (or the trunk, or have the "horn" signal go off, or
whatever!)
(Editor's Note * It works fine! We tried it out and it unlocked our car
over a cell phone!) Distance doesn't seem to be a factor.