In-camera chroma key (for reference)

[PunkMetalDrummer17]

What about an in-camera chroma key feature, that allows you to view say a background your going to drop in at post, on set. That way you get an idea of what your final composite might be like. To get something decent the camera would have to have in-camera motion tracking, but even without that just laying in the background for on-set reference might be nice. (But that does mean backgrounds would have to be done before filming.) You could also run the material (Both background and live action.) to a second tape deck or something, to use in editing so you get a better idea of how it would cut in. I know you could just drop in the background in post but I mean for heavily based CGI composites, atleast get the background in there to edit, while the original material (without background.) goes off to the effects house.