BitID is a secure way to provide user authentication using your bitcoin private key and a wallet that is BitID enabled.
BitID is an open protocol anyone can implement, check it out on github.
As a website developer, you simply ask a user to scan a QR code during the sign up process. As a website user, after you've signed up, its a simple matter of scanning a QR code to log in. No usernames or passwords are required!.
This demo uses websockets (rather than ajax polling) to facilitate communication between the webserver and browser. If you dont see the QR code transform into a green tick after a success message in Airbitz, you may need to move to a different platform.