Found on the Internet in November 2003
This only applies to people who own cars that can be opened using a little remote that attaches to a key ring who locked themselves out of their car and left the remote at home. Did you know that you can open your car door with your cell phone? There are actually four different ways you can do it -- all of them really simple!
The first way: Use your cell phone to call someone who has access to your car remote. You should call the person's cell phone or, if they aren't answering their cell phone, call their land-line phone and have them get a cell phone and hold it up to the non-cell phone. If you don't have a cell phone or it's locked in your car with your keys, use a pay phone to call someone who has access to your cell phone to bring it to you. Hold your cell phone about a foot from the car door and have the person who you called on the phone put your remote near the phone (the one they are using) and push the "unlock" button. Your car door will unlock. If they push the panic button instead and set your alarm off and you can hear them over the phone laughing like an idiot, make a mental note to kill them later.
Remember that if nobody is in your house and you need them to get in to get your car remote, you can let them in through your garage by calling them on their cell phone and having them stand outside your garage while you activate your garage door remote into your cell phone.
The second way: Use your cell phone to call AAA or a locksmith. They will come out and unlock your car for you. (Tip: You can also do this if you are not locked out but are just really tired.)
The third way: Use your cell phone to hammer on your driver's side door window until it (the window) breaks. Reach in through the glass and get your keys.
The fourth way: If you have a convertible and the top is down, climb over the trunk and into your car where the keys are. You can even do this without a cell phone!
Behind the Legend
This bit of information is nothing more than an update of the old trick of triggering intermittent wipers over an intercom.
Because a modern digital telephones tone reproduction is mathematically perfect, all sorts of signals can be sent over such a device. For example, you can call someone on a cell phone and have them hold their cell phone up to a pay phone and dial the pay phone by dialing your cell phone which sends telephone true tone through your friends telephone and into the pay phone. This is a handy way to have someone phone someone when you don't want them to know their (the other person's) phone number, and illustrates why the above-discussed method #1 for opening a locked car door works. Methods #2 through #4 are much easier to understand, and generally a little visualizing and experimentation will suffice.
If you locked your car with the radio on, you can also call the radio station that the radio is tuned to and ask them to put you on the air, then trigger your remote into your phone. The signal will come out through the car radio, unlocking your car and anyone else's car who happens to be tuned to the same station and has the same unlock code as you (only a 1% chance).
So far, we have only discussed the remote remote triggering of devices over a cell phone using radio- or sound-based remotes. However, taking this a step further, those with picture-capable telephones can transmit signals from infrared remotes, such as those used for televisions, over vast distances. The procedure is essentially the same as it is for sound-only remotes, but in this case the remote's emitter is pointed a the phone, which snaps a picture the moment the remote's signal is sent. If you timed everything perfectly and the receiver has their picture phone pointed at the television (or whatever) in the instance the image is received, the instruction will be properly transmitted.
The more clever of you will already have realized that, by reversing key parts of these instructions, one could dial their cell phone using their car remote, but we are unsure what practical purpose there would be in doing that.