For me the killer feature of Zim is the native integration with Git. It's super easy to write and commit, write some more, commit again. You don't even have to leave the editor interface.

I've coupled this with git pre-commit and post-commit hooks which basically ensure that the changes are always pushed to GitHub.

I've found a similar application for Android called GitJournal. Unfortunately it doesn't do the wiki syntax which Zim recognizes. Only markdown and plain text. So I have a separate repo for my mobile notes. They're usually much shorter anyway, the type of notes you'd put on a sticky.

Hopefully one of these tools will learn the format of the other in the future. That would allow us to use both of them on the same repo.