In the future there will be no more keys, or better, they will not exist in the way we view them today. In the future, your own hands will be your key ring. We already know systems for access control, which are based on a fingerprint scanner. It has been designed, however, by AT&T Labs, the prototype of a system that transmits vibrations through the bones of a user which, collected by a receiver installed in a door handle, allow to automatically open the door as soon as the specific user touches the handle itself. Using piezoelectric transducers, the system could one day be integrated into smart phones or wristwatches to create doors that automatically unlock when the right person touches them and that remain, instead, tightly shut when someone else tries to enter.
Such a system works on frequencies that humans cannot hear, but tha they could perceive in a very quiet room. These acoustic signals travels from a piezoelectric transducer through human bones almost like the sound waves vibrate through the skull and inner ear to allow our sense of hearing. The vibrations travel through the body straight to the hand, which can send the signal to everything it touches. Putting another piezoelectric transducer in the handle of the door, that would be able to identify the person who touches the handle, letting only authorized persons enter.
Researchers which are developing this system have also found that different skeletons, with different bone density and lengths, would transmit the acoustic signals in different ways. This means that only the right combination of signal and skeleton can open the door. In other words, if someone stole the phone and wanted to use it to open your car or door without your unique skeletal fingerprint added to the signal, he surely would not succeed. Moreover, researcher are also studying a system that would send emails every time someone tries to enter a building without authorization.
All that is truly amazing, especially considering that this technology may not stop to the locks but it could also be used for cars or even computers or any other device that needs access control.