For authentication, I'd make it so that when the professor each session, the class is given a random 4-5 digit code. That way the students would have to be in class to get the code and participate.
You may also want to think about adding the ability for the instructor to add different buttons, not just "understood / confused". You could then have class polls, or group questions to see how many people are paying attention.
This should all be able to be controlled from the instructor dashboard.
okay class, we just went over big-O. here is an algorithm... what do you think the big-O of this is: O(n), O(n^2), etc...
Nothing that you'd have to keep track of the answers for longer than the length of the class.
Plus, if you added logins, that would just make it that much more of a setup / hassle to get classes going.
That said, this is a great idea. This is the kind of real-time feedback that I would love to have access to. Many of my students would rather fail than put their hand up and ask for help. Something like this would really help them out.
I like the idea of the code to authenticate students. I guess you'd have to watch out for selection effects in all of this too... an interesting challenge!
Great suggestion, producing a report is a great idea. I could even use the confusion data to predict exam test scores.
If students are going to be evaluating their teachers (providing richer feedback than confused/understood), then you're correct there will have to be authentication for students.