Flipgrid is a video response platform where educators can have online video discussions with students or other educators. Teachers can provide feedback to students AND better yet students can provide feedback to one another. With Flipgrid One (Free) you get one grid with unlimited topics. So if you have multiple classes or subject areas you can just create a different topic for each and share that topic code. With Flipgrid Classroom ($65 per year) you get unlimited grids, topics, responses and replies to responses.
Flipgrid works with virtually any device with internet access, allowing students to respond, visually to class discussions. The list here is very helpful on giving you some ideas to get started.