Unlock your car using mobile phones

Does it ever happen to you that you forgot your keys inside the car and then locked the car. I have been in this type of problem couple of times and then used to look for a mechanic or a person who can open my car's door using some scale or something.

One of my friend told me a rather easier and technological way of opening the car in this condition.

Pre-requisite:
Car should have remote locking (with sound based remote control)
The duplicate key should exist with someone else at home who has a mobile phone as well

It is easier and most likely, right?



Steps:
1. Call the person who has the duplicate keys of your car.
if your duplicate keys are at your home, you can call your friend, parents, spouse or servant or whomever is near the keys.

2. Ask the person to get the duplicate keys and hold its remote near the mic of their mobile.

3. Set your mobile to speaker phone. Stand near the steering side of your car.

4. Tell the person to press the unlock button on the duplicate keys while holding it near their phone/mobile.

This may not work immediately, so ask them to tap the button continuously till your car unlocks. Certainly this has worked wonders for me few times, but I am yet to understand the technology behind this. Will it be possible for any electronics and communication engineer to explain, if it is a desired behavior or it is due to never though before defect (security Threat) in the system??