I was discussing QR codes just yesterday with another AM at Victor Chandlers!
We recently made changes to our own landing page promoting our Mobile Betting platform. We changed the destination URL for affiliate links from the standard to a revised version for affiliates that stressed the importance of signing up their account
first and
then accessing the mobile platform, thereby securing the referral for the affiliate.
That said, I think that route is a poor second - you want to be able to refer players from a mobile device in a way that ensures you get the credit - that's a far better player experience than asking them to put the mobile down, boot up a PC, sign up and then go back to a mobile.
If you're still keen to use QR codes then I can recommend this site which has a decent QR code creator:
http://keremerkan.net/qr-code-and-2d-code-generator/
In my tests yesterday by converting an Income Access generated tracking link to create a QR code the three accounts I registered all tracked correctly. I'll be doing some more testing this week to confirm.
I think there's plenty of scope for affiliates to start dropping banners on their pages and replacing them with QR codes for smart phones.