Came here to say this. I use org-mode to do what OP's package is doing. But OP provides some features like

> one keystroke executes all specially-marked lines from a buffer and inserts the results inline

Not sure if we can make such specially-marked lines using org-mode. Never needed this feature myself. But for those who want a workflow like this the new package could be useful. But again maybe there is a way to do this without an external package with a little bit of elisp?