I can't think of any actually useful applications (the one given only makes vague sense if you pretend bluetooth doesn't exists), but it's a cool demo anyway and the linked blog posts are excellent.
If someone is interested in how we got an amazingly small QR using base-91 and some other cool methods here is a good read with demo code
https://docs.google.com/document/d/1B7AJDVu5ei6c7ZuHRiTvQ_q8...
User confusion and the fact that high quality camera tech and OCR aren't exactly cheap.
But I agree it's more interesting from a technical point of view over a practical one...
I could see this being used to share diagnostic information, certificates,condensed instruction manuals, &c.
However, adding a small lcd display allows the presentation of human readable data as well, and many devices already have screens on them.
(I always thought serial over TRS (headphone) cable would be an interesting option as well.)
BT/Wifi methods will broadcast data to anyone within radio range, but optical data exchange like this can take place under your coat, or using some easy means of protecting the transfer against 3rd party listeners.
Some applications from the top of my head.
1. Access to buildings/restricted areas etc. can be made more secure, by using higher data content with animated codes, foregoing the requirement of the device having an internet connection. 2. Transfer data to a large crowd of people, say at a concert, etc. 3. Pairing of devices where one device cannot have bluetooth or other wireless hardware (due to power / security constraints)
Honestly, this is another channel of communication between devices and it's exciting.
data distribution over normally visual broadcast channel (TV -> mobile device, billboards -> mobile)