Could you give some concrete examples of the types of data that an existing smart monitor (not a TV) collects and sells to others? (Ideally also naming the manufacture and the device.)
Due to this, I have my own specifications (not fully written, although I did write a lot of it), which are much simpler than HDMI. (It has digital video (with no inherent picture size limit, although implementations would be limited), analog audio, and an optional IMIDI (which is a two way command stream; it is safe to avoid connecting it). The IMIDI can be used for captions as well as for control, and can also be used with IR, as well as with the special IMIDI port.) (These would be fully free, although there may be trademark licenses (perhaps to avoid many of the problems that HDMI and others have) but no other restrictions.)