This may come very useful in handy someday. Good reason
to own a cell phone also. If you lock your keys in the car and
the spare keys are at home, call someone on your cell phone.
Hold your 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.
That 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.
Source: www.chip-india.com