I saw that @KarlHegbloom has started to implement a few new features, some of which have been merged here.
I was wondering if we perhaps were duplicating some efforts, because I have also done some quite extensive rewrites of mplayer-mode which might benefit others. I'm still not really sure about which of them might be reasonable to include in mplayer-mode and which should be viewed as making it too complicated, as mplayer-mode maybe should be a somewhat small and simple package.
So this issue is to open a little discussion about it.
The use case for which I implemented this was transcribing research interviews, and writing it in structured org-mode-files.
My somewhat messy development history can be found in this branch: https://github.com/andersjohansson/mplayer-mode/tree/org-sessions
The main features I implement are:
- Session saving and resuming, either in file-local variables or in org-mode properties
- Modeline display of play/pause status and current position in file (rightmost in screenshot below). This has been buggy from time to time but I believe my last changes to this feature made it non-interruptive.

- Timestamps written to org-mode links. Apart from looking quite nice by default, this has the added benefit that clicking on a timestamp takes you directly to the right position in the right file.
So, @markhepburn, do you think that any of this would be good to integrate in mplayer-mode (and do you have time and energy to think about this at all, I don't expect anything from you, really)? It's a tighter integration with org-mode, which could be helpful for some, but perhaps should be optional. Some of the features could probably be provided in an auxiliary package, I haven't thought that through.
Well, thanks for all your efforts so far, mplayer-mode has helped me a lot.