Justin Hunt recently updated the Poodll Feedback mod which uses multimedia as a the means of providing students feedback on submitted assignments.
Using the PoodLL feedback type it is possible to give audio or video feedback, or even draw a picture feedback, on a student’s assignment.
Grab the download at https://moodle.org/plugins/view.php?plugin=assignfeedback_poodll but note that this is part of a much larger set of Poodll addons (including the Poodll assignment upload).
Below is a video that highlights the recording by students for the assignment, in the feedback module the teacher essentially gets the exact same tool. Direct video link: http://www.youtube.com/watch?v=L59vtxaTKoQ