Poll Everywhere can be used to gauge the level of understanding of the students in your class through real time individual responses, in addition to a useful alternative tool, for enabling the whole class to answer the same questions. Polls, or questions can be set up in PowerPoint of Keynote where students response via their mobile device, the response is instantly displayed on the poll.
An alternative to setting questions is through an open ended word cloud where students can post their questions or thoughts during the lesson. All the comments are displayed on the board and can be addressed throughout the lesson by the teacher or the students supporting each other.
I have found Poll Everywhere particularly effective as a brain storming activity again using the open ended format. Students them post their ideas and thoughts which are again displayed in real time, which facilitates the most timid of students to response and submit a response.
The video opposite is a short how to guide of how to set up and run a Poll.