ALPHA! Barely works. Work in Progress!
Run a command interpreter (AKA a REPL) in a text buffer inside atom. Basically a port of emacs's comint-mode.
Running a shell inside your editor (but in a text buffer, not an ANSI terminal emulator) is the best thing since sliced bread. As far as I'm concerned, it's THE killer feature of emacs and the reason it's taken me so long to switch away from it. Atom needs this. I hope to be able to bring it.