A fantastic real-time tool for formative assessment.
Plickers is a web based service where you can store multiple choice quizzes. You can then quiz your students in class and get instant feedback using the app (which runs on iphone, ipad or android). Each student has a unique Plickers card which they rotate to show their answer. Sweeping across the room with the app records the student and their answer and graphs the data instantly. No photographs are taken. A short video tutorial is here https://www.youtube.com/watch?v=bejiz2HzUz8 and the plickers website is here https://www.plickers.com . Free accounts are limited to 5 questions per set. I get each pupil to glue their personal Plickers card into their book at the start of the year, fresh ones can easily be printed as spares or for finished books.
Differentiation / Extension:
Once you are familiar with the software inputting questions is so fast you could have pupils write them and add them to the quiz.
You can opt not to show the correct answer each time but have pupils correct work.