I'm not sure what scale you mean. The demo I saw involved 100+ students in a crowded low-income rural Indian classroom with one teacher. The qrcodes were printe

I'm not sure what scale you mean. The demo I saw involved 100+ students in a crowded low-income rural Indian classroom with one teacher. The qrcodes were printed on regular paper on an inkjet printer. The image recognition software ran entirely on a cheap desktop with a webcam. The whole thing was designed for that type of environment. I doubt it will be used much -- teachers who care seemed to be in even shorter supply than the minimal tech needed to run this -- but the guys at MSR that created it had put an surprising amount of work into making the image recognition fast and efficient. They had a smartphone-only version too, but it had some limitations, if I recall, because the processing power just wasn't quite there yet.