New content type - Drawing

I wonder if there is any development of a tool that allows students to draw/write freehand on screen? This could be a part of many exisiting tools (eg interactive book, course presentation, column, documentation tool etc), or standalone. Sosmethign that could be used both synchonously and asynchonously.

Ideally, being able to use it both on an individual and collaborative basis would be terrific. When individual, the student content should be saved so teacher can view. 

Capacity to upload backgrounds in the form of scaffolds, diagrams etc would be of benefit.