Match My Sound™ is primarily an audio tool but it also has video features. Some MMS (or Practice First or Achieve Music) users may have noticed content that has a linked video. It's great for learning if the students see how something is performed. However, this video here demonstrates an experiment with letting the student record audio and video simultaneously and submit both to the teacher. All beautifully synchronized with the sheet music.
So who could use such a feature? There are in fact no musical instruments I can think of where seeing the student performing would not provide any information to an experienced teacher. Sure, some instruments are more 'graphical' than others. Think about the guitar or piano. At the same time, seeing the posture of a singer or the playing position of a wind player can also tell a lot. If not more then at least it helps to track down some of the mistakes that may be caused by factors that cannot be detected aurally.