Are there any mobile phone apps that would allow for students to anonymously "buzz" me in real time? What I have visualized is a free app students can download that features a button they can press that will signal me by making a light blink on a website. A noise might be distracting.
This would be especially suitable during the days where I teach more difficult topics. On certain days I anticipate more, maybe smaller confusions. Only some students feel comfortable asking questions, and those that do often will limit themselves to one or two.