New at some of this so please bear with me.
I have a potential client that wants to produce a video seminar in which he is standing in front of a large map. The idea is to use a chroma key background, a video mixer and a monitor so he can see the map in relation to his position similar to a wetherman. The problem I need to solve is this: he writes on the map in his actual presentation and wants to be able to do something similar in the video.
Since this is a rather low budget project, I want to use a simple mixer like the Sima SFX10, one camera for the subject against a blue screen and one camera for the map. I will then output the composit to a monitor for the subject to look at and another output to a DVR. I cannot determine what I need to allow the subject to "write" on the map.
Any help or suggestions would be greatly appreciated. Thank you.

