Website: https://github.com/nelhage/reptyr
Quote:

reptyr is a utility for taking an existing running program and attaching it to a new terminal. Started a long-running process over ssh, but have to leave and don’t want to interrupt it? Just start a screen, use reptyr to grab it, and then kill the ssh session and head on home.

 
I haven’t used it yet but I’ll definitely keep it in my tool box.