For me QR-codes are great because they are mysterious (at first) and students find them interesting. And I’m saying this after having actually tried it in class. I printed out the codes which had links to some resources and passed them to my students and asked them what those were? Some of them knew and told the others and I reckoned at least 30% of them used a smartphone to access the url and messages that I have created. (This was an undergraduate class and so the students aren’t barred from using their smartphones.)
On the other hand, a smartphone or in my case the i-pad is not so good for writing. Because the device is so convenient, I hardly power up my laptop at home any more. I do almost all my reading on the i-pad and that’s great but it’s just reading. I find it a chore to type on the ipad so there is practically no writing or blogging. And it took something as funny as the justinsomnia story to jolt me out of my blogging inertia.