it wont work. its impossible.
remote unlocking keys use radio signals to communicate with the module inside the car, telling it to unlock.
radio signals cannot be transmitted across phone.. only sound waves....
here is a big explnation i copied from somewhere, coz im too lazy to type shit out lol
The letter's basic premise - that you can 'beam' your car's remote lock signal through your cell phone - is the primary point of contention. The technology behind both cell phones and door likes provide the strongest argument that this should not work. While both your cell phone and your key chain remote are based on radio transmissions, they operate on very different frequencies.
Your remote door lock keychain remote works by emitting a low-power radio signal to a receiver in your car. The signal is encrypted specifically to work with your vehicle and is very hard to duplicate. Cell phones use a higher-powered and higher-frequency radio signal (800 MHz and up, whereas your remote locks operate between 300 and 500 MHz). Cell phones transmit voice and data – they cannot "carry" other radio signals, which is what this letter is suggesting (unless the author was foolish enough - or thinks you are - to believe that your car lock remote works on audible signals that could be 'broadcast' through the phone's speaker).
Nonetheless, I've had many readers write me to insist that it is possible to unlock your car doors from a great distance using cell phones - most with first- or second-hand accounts of trying it successfully. Few provide details about their "experiments," and among those that do, it quickly became obvious that they were making the critical mistake of failing to ensure that they were out of the normal operating range of the remote transmitter. There are many more accounts on numerous message boards of people who claimed to have tried it and failed.