[k2enemy]

I'm looking for the same thing as you.

On a mac, VooDooPad fits the bill but it is not open source and its future looks murky. If it were open source with an active community of users I think I would use it.

This has kept me on vimwiki with .md extensions so that vim will at least do syntax highlighting for markdown. You can easily link to local multimedia files, but they don't display inline. As a bonus, a diary entry for the day is just <leader>w<leader>w away.