Nice concept! Although I can imagine this only works in large classrooms, as where I'm used to have pretty small sized classes (~30).

I have had the opportunity to experiment with something like a voting system. The teacher mixed his lecture with some (multiple choice) questions the students can answer via the voting system. This created a far more dynamic lecture with instant feedback on the answers provided. Maybe a feature you want to consider? Because with the smartphones and tablet these days you eliminate the need for an extra device (like we were experimenting with).

Besides this all, the site looks broken here (Fx 12.0, Vista) because the CSS is not loaded. IE8 in Vista is also messy (with a loaded CSS file).