It's a QR-based system, but according to that page it says it can work via a tap or click on the QR code, too. So you don't have to point a camera at the QR code.
Wordpress, Android, .Net Client, Node, PHP, Ruby, Windows Phone, and Haskell. Unfortunately, having people download an app to login to your website kind of ups the bar a little. Still, they can just scan the code with their phone as well.
https://fidoalliance.org/adoption/video/how-the-nok-nok-solu...
Or this maybe: https://www.grc.com/sqrl/sqrl.htm
It's a QR-based system, but according to that page it says it can work via a tap or click on the QR code, too. So you don't have to point a camera at the QR code.