I am preparing a presentation that will cover the Mobile app and plugin support. The plugins database has a badge that shows 5 of them and you can see that list here
However there are some that have not been added yet and some that are not in the plugins database at all. If you are working on Mobile support and think it would be at least demonstrable would you post a link here so I can at least mention it in my presentation.
Here is the list of Github repos to those I have found so far.
If you were thinking of adding mobile support, it got much easier with the release of Moodle 3.5 and you can find some documentation here