It's quite cool. Industry is so legacy and lazy. Those sort of things should be already "present" years ago.
There was FirstLight (I think) programme which made a use of it. You could open video with it, do adjustment and if you had this file loaded in some player or NLE change were visible straight away.
Matada or rather active metadata is something very underestimated in my opinion. We still can't even pass properly simple things like color space etc properly, so maybe active meted is just to much
David's (guy who wrote Cineform) ideas were just to much ahead of the time and lacked support+money from bigger company. Even so he did manage to make it SMPTE standard.