Blue2Factor

Blue2Factor authenticates users without any user interaction by verifying that the device that is being used to sign into a domain is in close proximity to one of the users other devices. For example, if a person is signing into a domain on their computer, Blue2Factor makes sure that their phone is nearby. Authentication is instantaneous so users can be validated each time a domain is visited. And unlike other 2FA solutions, Blue2Factor is immune to second factor phishing.