I made this image more than 5 years ago. I posted it to /r/somebodymakethis
It seems appropriate to mention this around now. It appears somebody did. My motivation wasn't to stake a claim on the idea but to encourage it and hopefully prevent someone else jealously guarding the idea as their own private creation. Since I made the image, there have been a few active styluses turn up as third party devices. I doubt they copied my idea. I think it is more likely that it is a logical advance on touchscreen devices.
I haven't seen a great deal about the Apple Pencil yet, but I hope they have fully explored the potential beyond just a precise pointing device with pressure. The ability to use a stylus and a finger on the same surface and to be able to distinguish one from another adds a lot of options for user interface design. I mention in the image text a few of the possibilities I had imagined.
A program like SculptGL could make excellent use of fingers and stylus together. Rotate the model with your fingers and shape it with the stylus.