Spotted by Android Police, this feature, called “Easy Unlock”, is by default disabled, but people running Chrome OS on the dev channel can enable it with chrome://flags/#enable-easy-unlock.
It is still not known what kind of technology the unlock feature would use for sensing the Android device proximity. It could be Bluetooth, Wi-fi or even Near Field Communication, which although Chrome does not support at present, is being worked on.
Like I said, no one knows what type of connection it will be, because the feature doesn’t actually function yet. There is only the setup and description for now, and even that is still unfinished.
This is a great idea, but Google didn’t come up with it. There is a desktop utility called Blueproximity that has been around for a few years.
From the project’s Sourceforge page:
This software helps you add a little more security to your desktop. It does so by detecting one of your bluetooth devices, most likely your mobile phone, and keeping track of its distance. If you move away from your computer and the distance is above a certain level (no measurement in meters is possible) for a given time, it automatically locks your desktop (or starts any other shell command you want).
Once away your computer awaits its master back – if you are nearer than a given level for a set time your computer unlocks magically without any interaction (or starts any other shell command you want).
It is also a similar concept to the electronic car door “unlock with key fob” gimmick.