I am doing quite a lot of work inside tmux. I especially love that I can start multiple windows/panes and use them to run the same thing across multiple servers, while still having normal shell access between steps.
This thing was greatly improved when I wrote tmux_send_to_many, but one thing was missing – waiting for the thing, running in tmux window to end.
Generally, I had to look at all the windows, and decide when to launch next step on my own.
Not anymore.