This is possible with the C Camera API. You would use the same process as the FaceFilter demo, but to do a timestamp you would have to replace the bits of the preview frame where the numbers would go with your own custom bits. There aren't any samples or docs that show how to do this, as far as I know.
That's assuming you want to encorporate that into the video file itself. If you just want to overlay some stuff on the screen, it's a simple as putting another Cascades component where you want it.
Paul Bernhardt
Application Development Consultant
BlackBerry
@PBernhardt
