Backchanneling in the Classroom?

I was first introduced to public speaking backchanneling when I attended a session by my district’s technology coordinator, Ryan Collins, at eTech Ohio’s 2009 conference.  During the session, he used several different backchanneling methods (I don’t remember the specific services.) to relatively instantly gather background information about his audience.  Additionally, he was able to provide a medium that the participants were able to submit questions or reflect on comments he has made during the presentation.  Essentially, it was instant (and silent!) collaboration.

The thing I noticed most about this, was that all of the participants in the backchanneling process had to be completely engaged in the presentation.  That’s what I strive for EVERYDAY with EACH of my students.  Admittedly, the extent of engagement in my classroom is all too often listen-to-what-I’m-saying-and-write-it-in-your-notes.  Bleh.

So that’s where the idea of students backchanneling to me (I’m not sure if I used the verbiage correctly there) during lessons comes in.  Has anyone used this successfully?  What services are available?  Which are better than others?  How can one student backchanneling be beneficial to all my students?  Are there some hidden benefits here for absent students to utilize?  Other thoughts or advice?