Hi,
Maybe there are some R users wandering here, so I allow myself to announce that we just published a new R package on CRAN (the R package network), called robservable, which allows thanks to the Observable API to use a notebook as an HTML widget in an R session, Shiny app or Rmarkdown document.
The package allows to include and display specific cells, update cell values from R, and create observers to be used as inputs in Shiny. It is still young and has some limitations, in particular there is no offline support (the notebook code is accessed via the API each time it is displayed), and the inclusion of unnamed cells is possible but can be a bit tricky.
For more information, you can take a look at the package website :
You will find in particular a small gallery and an introduction vignette.
The package has been developed with Kenton Russel.