EnClicker is a simple “Clicker” system supporting both mobile Web and App. A teacher can create questions and publish them to his/her students. Then, students will follow the teacher to solve the questions that their teacher created. The results (students’ responses) will be shown on the teacher’s page.
Start with iOS app, or Android app, or Web: einbrain.com/enclicker (No longer available)
Clickers are an interactive technology that enables instructors to pose questions to students and immediately collect and view the responses of the entire class. This is how clickers work: Instructors present multiple-choice questions (verbally or with presentation software or with the i>clicker software).
https://clickercounter.org/