I used QR odes for the same sort of thing, but Firefox sync has gotten so good at sending tabs to specific devices, including a desktop that might not have a convenient camera, that it's even more convenient.
KDE Plasma provides a QR Code for anything not too big you copy-pasted by clicking on an icon. "It should be more convenient than using the computer as a Wi-Fi hotspot for the phone, which is a two clicks operation, right?"
Wrong. It was painful.
We should reuse the idea of Quiet.js, seen today on HN [1], to solve this kind of situation.