`jrnl` commandline tool does the same with a text file. You can sync it with dropbox and use the same journal across multiple machines.

Thanks for the hat-tip on `jrnl` - this is a much better version of the cmd line tool I talked about in my comment above and I am now starting to use it. Great logistics being cli-based, think I'm going to be using it plenty.

Nice one, thanks! Mine was for a more specific use case but this could be really helpful.