BTW do people use tmux/screen to start multiple apps for development?

I'm looking for a way to start nginx/sass watcher/js builder/web app in a split screen, and also stop them all with one command (which would send ctrl-c to all windows). Now I just use tabs (OSX).

This is the use case of Foreman. https://github.com/ddollar/foreman

or Goreman. https://github.com/mattn/goreman