I'm liking this:

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.