well, I thought about doing a video chat over some game play, so two friends could play a match of anything while having a video conversation, next day some one posted something similar here on HN.

I then thought about drawing on top of the video stream so you can use as like one os those games where you have to guess what the other people is drawing or, to coach someone one to one and being able to "comment" on their screen as they speak, but again, I'm pretty sure every video chats does that. So I left the idea on the drawer for now.

https://www.youtube.com/watch?v=yS3_CRr7tys (draw on the stream)