Last week, Microsoft published a roadmap for Windows 10, listing features that are in development. Two of those features were the ability to unlock your PC with your phone or with a companion device, such as a Microsoft Band 2.
The feature will be known as Windows Unlock and will be powered by the Companion Device Framework, something that the firm went into great detail about on MSDN. The documentation lists the kinds of devices that can be used, the security measures taken, and more.
There are four different use cases listed:
Attach their companion device to PC via USB, touch the button on the companion device, and automatically unlock their PC.
Carry a phone in their pocket that is already paired with PC over Bluetooth. Upon hitting the spacebar on their PC, their phone receives a notification. Approve it and the PC simply unlocks.
Tap their companion device to an NFC reader to quickly unlock their PC.
Wear a fitness band that has already authenticated the wearer. Upon approaching PC, and by performing a special gesture (like clapping), the PC unlocks.
While it's always nice to have additional options, it's not immediately clear as to why most of these would be more convenient or more secure than typing a PIN or allowing Windows Hello to recognize your face.
The documentation also lists three user signals. For the feature to work, the device must utilize all three.
Intent signal: Allows the user to show his intent for unlock by, for example, hitting a button on the companion device. The intent signal must be collected on companion device side.
User presence signal: Proves the presence of the user. The companion device might, for instance, require a PIN before it can be used for unlocking PC (not to be confused with PC PIN), or it might require press of a button.
Disambiguation signal: Disambiguates which Windows 10 desktop the user wants to unlock when multiple options are available to the companion device.
To put it simply, the intent shows that you want to unlock the PC, the User presence shows that you are the one physically doing it, and the Disambiguation shows which specific PC you wish to unlock. The signals can be in the form of an action or a gesture.
Of course, all users have different needs. More options tends to be the best path toward pleasing everyone.