ungulate-mode, an Emacs minor mode to send your Python buffers to Rhino with minimal hassle. Basic usage is in the source, but since it’s intended for existing Emacs users you should have a look there anyway. It’s pretty simple, lacks autocompletion for now, but maybe it will come in handy for someone out there (I imagine the intersection of Rhino and Emacs users is small). Feel free to submit issues, etc. with ideas for improvement.
I haven’t really been keeping up on all the latest developments around here but it looks like there is some exciting stuff going on with respect to plugin development on Mac. A few years ago I hacked together this little thingy to run commands from a remote shell but it wasn’t very useful for more than testing out a command or two. Then a few months ago Rhino for Mac got the
StartAtomEditorListener command which made writing Python for Rhino almost pleasant, until Atom crashed for the nth time and I longed to go back to Emacs. Earlier in the week I had a need to write a couple of scripts and figured it wouldn’t take much work to be able to do it in Emacs.