I think someone mentioned this in class. The third grade teacher I work with is using Class Dojo and the students love it. I think she has it as a free app on her phone, so as she is walking around the classroom she can give either the whole class, or an individual student some positive reinforcement. She uses just the positive reinforcement buttons, but there are negative behaviors that you can identify as well. You can type in any positive or negative behavior you wish. I think this looks very motivating for students. I would use it on my phone, too, rather than project it because I think it can be very distracting for students to see the avatars and hear the bell ringing when the teacher reinforces a student's behavior.