While in class, a teacher is watching her students at all critical times such as when she is explaining some key concepts, demonstrating some important procedures, trouble-shooting some common mistakes and so on.
In online learning, what could function as such a teacher's eyes? Some in-text quizzes to check on their grasp? Some webcam or screen-sharing technique?
When a critical mass of students are not paying proper attention to what she's presenting, she has means to direct or redirect their attention.
In online learning, what could work like such a teacher's mouth? Skype? Some audio clip, or alert boxes, or banner scrolls?
How do we answer such typical teacher's concerns as:
What are the students listening?
What are the students hearing?
What are the students imagining?
How can we track the students' eyes, gestures, and thoughts?
I recommend jQuery & co.