Using your cell to unlock your car

I recently read about an interesting way to unlock your car. Apparently, if you can't find your key, or your keys are locked in the car, & you have a keyless entry, you can just call whoever has your extra set of keys, hold your cell phone up to the lock, & then have the person press the unlock button. Apparently, it doesn't matter how far away you are from the extra set of keys. I thought this must be an urban legend, no way can that work. What the car hears itself being unlocked?

So, I made my family test this out, because I didn't want to put on shoes. Sure enough, it works, although the cell phone needs to be held quite close to the lock. I don't know how it works, magic probably.

I do reccomend giving this a test before locking your keys in the car. Unfortunately, it's still no help to me because my car doesn't even have automatic locks. Someday, someday.