Today's Meet has been a popular backchannel tool for years but is sadly closing its doors in June 2018.
While looking into alternatives I discovered Sli.do which offers a variety of interactive tools that might work well in your classroom and/or professional development.
I share a quick overview of Sli.do in the video below.
Also! One of the things I forgot to mention in the video is you can see the results from open-ended questions in a word cloud!