@Ladoga, I remember that there was a way to capture camera frames with gstreamer on the N900, specifically screen-sized ones. Writing a shell script to run the command should be trivial, and the command should work on the N9 too. This fulfills all your requirements and is easy to implement. I suggest you search for the relevant command and if you are not familliar with shell scripting, start a new thread asking for help. The result will be useful to many people.