Not sure if it's small, but here goes.
In vim, Sublime Text, and others (osx textmate I've been told) you can set an option that will save the file in the current frame when it loses focus. While googling to check if Emacs can be configured to have the same behaviour I found that XEmacs has a 'deselect-frame-hook' that could be used for this. From the same googling, I found that Emacs would require something beyond a mere elisp module, but it would have to be implemented in the core C code itself.
I would really like this option, since I am "frame oriented". I tend to have quite a few frames open and use "focus follows mouse" which is available in any Linux desktop. I move my mouse to a terminal window to type 'make' or run the python/bash/what-have-you script and I would like emacs to save at least the buffer of the frame I just left and perhaps even all buffers (but since they wouldn't have focus anymore, they'd already been saved anyway).
Ian.