Microsoft is currently testing a new version of its Authenticator app for Windows 10. Twitter user WalkingCat discovered the app, named "phone sign-in beta." It appears the updated app will allow Windows 10 users to unlock their machines over Bluetooth, simply tapping the machine from a list to unlock it.
Microsoft has been introducing new ways to sign into Windows 10 PCs without a password, including Windows Hello support through fingerprint readers and cameras. This latest Authenticator app is currently in internal beta testing at Microsoft, and it appears to be limited to Windows 10 Mobile devices. Microsoft doesn't currently offer its own authenticator app for iOS or Android, so it's unlikely we'll see a similar version across all platforms.