I love to use flipgrid. I will post a question and look for students to respond by recording themselves. It works great with groups of students or individuals. I use this when the students have to design and and explain their student designed experiment methods.
They English teacher uses this and really likes it also. She has a difficult time getting some of her students to do it though because they don't like to be recorded. However, some of this kids are the same ones who take nonstop selfies.
I have heard of flipgrid and am going to try it out with my students. I think it will be a great way to check their comprehension. If I give them a questions about an article they read, then they can answer it on flipgrid.
Flipgrid is great! We use it as a way to promote our classes and activities for incoming freshmen. Students/Participants and Teachers are involved and find it fun and rewarding.