Sometimes it does take a bit of time for things to filter through, no matter how many times I read them on the numerous blogs I subscribe to. Backchanneling tools definitely come under this category. If it's news to you here's an overview from TodaysMeet:
What finally convinced me to sit up and take notice of this resource was witnessing its use in an inspiring lesson where learners were watching a film and using TodaysMeet to express their thoughts and ask and respond to queries. The teacher was following the stream and was able to feed in comments to alert them to important upcoming sections that they should pay particular attention to or things to listen/watch out for.
TodaysMeet was the tool of choice, and although there are alternatives (for example Twitter or Google Moderator could be used in a similar way) it's the very simple, no-signup, streamlined interface that lends its appeal. Furthermore, transcripts of the backchannel can be saved as a pdf for future reference.
Each new topic is assigned a unique url and the backchannel remains open for up to a year.