On a historical note (and most of it has come to pass, though maybe not in the way they wanted it, and certainly not as "unified" as they conceptualized it), check out the Xerox PARC project that was termed "tabs, pads, and boards":

https://norrisnode.com/tabs-pads-and-boards/

http://lowendmac.com/ed/rosen/10ar/ubiquitous-computing.html

https://www.ics.uci.edu/~redmiles/ics203b-SQ05/papers/Weiser...