Does your car have remote keyless entry? This may come in handy someday. Good reason to own a cell phone: If you lock your keys in the car and the spare keys are at home, call someone at home on their mobile phone from your cell phone.
Hold your cell phone about a foot from your car door and have the person at your home press the unlock button, holding it near the mobile phone on their end. Your car will unlock.
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 (or the trunk).
This is a HOAX! You can unlock your remote keyless entry enabled car from a long distance via a mobile phone call. A lot of people swear that the trick works while a great many others claim that it does not and is technically impossible.
I suspect that at least some of the people who claim that the Keyless Entry technique works have conducted their experiments without realizing that they are actually still within unlocking range of their vehicles. The range of the entry systems may be significantly greater than experimenters realize. Thus, people may actually believe that they have unlocked their vehicle via their mobile phone when they have in fact done so in the normal way via their remote device.
Keyless entry systems work on radio waves, not sound, so it is very difficult to believe that the unlock signal could be transmitted via a mobile phone call, especially since mobile phones and keyless entry systems work at entirely different frequencies.
Some have postulated that the technique might be possible with certain keyless entry systems and/or phone services or combinations thereof and this may indeed be the case. This scenario would explain why the technique might work for the few but not the many. Coupled with false conclusions made from invalid experiments, these exceptions might explain why so many people so vehemently claim that the trick actually works in spite of the evidence against it. What I can say conclusively is that I have personally testing the technique with several keyless entry/mobile phone combinations without any success whatsoever. And, even if the technique does sometimes work, it seems clear that in the great majority of cases, it does not, so this tip is actually rather pointless.