If you have a keyless entry for your car. (the button you press to unlock your car for the people who don't know what that is...) and let's say you locked your keys in your car.. And let's say back at home your parents room mates friends whoever has the 2nd pair of keyless entry to your car.. You can call them over your cellphone and hold your cellphone by your car and have them press the unlock button over the phone.

http://www.snopes.com/autos/techno/keyless.asp

That's a myth.