EnClicker is a simple "Clicker" system supporting both mobile Web and App.
EnClicker Manual: http://www.einbrain.com
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.
This App supports an anonymous mode (teacher and student) as well as a signed-up user mode.