From clickers to programs like Learning Catalytics—which data-mines to match students with discussion partners—student-response systems are becoming more and more sophisticated. But Liam Kaufman, a graduate of the University of Toronto, thinks that the key to effective feedback is a tool with fewer bells and whistles.

Mr. Kaufman is the developer of Understoodit, a browser-based app that lets students indicate their level of comprehension during class, and then see how much everyone else understands.

The idea is that, during a lecture, everyone runs the Understoodit Web site, which is also accessible via mobile and tablet devices. Students press buttons to indicate that they either understand the material or are confused by it. The feedback is displayed in real time, in the form of a “confus-o-meter” and an “understand-o-meter,” which show the percentage of students who comprehend the material.

The app was inspired by clickers, Mr. Kaufman says. But whereas clickers usually require students to answer questions so the professor can gauge their understanding, Understoodit lets them directly indicate confusion or comprehension, which is then available for everyone to see. That approach, he hopes, will encourage students to ask more questions when they realize that others are confused as well.

Mr. Kaufman first tested the app on an entry-level computer-science class at the University of Toronto in February. The app is still in beta testing, and available by invitation only. More than 2,000 people have signed up so far, Mr. Kaufman says, including professors at institutions such as Harvard University, Stanford University, and the University of Pennsylvania.