The other day, I discovered that vim has an “encryption” mode. In this mode, your file is encrypted whenever it is written to disk, and decrypted whenever it’s read back (this also applies to any temporary swap files).
I gave a presentation on Elixir at the London Ruby User Group in March.
I use tmux panes all the time. I’m always editing at least one set of source code in one pane, running tests in another and probably running servers and consoles in yet more.