I have an Automator workflow script, which uses emacsclient to edit any text, in my `~/Library/Services`. The service receives selected text in any application and output replaces the selected text. It consists of two parts: Run AppleScript, and Run Shell Script.

The AppleScript part is:

    on run {input, parameters}	
    	tell application "EmacsMac" to activate
    	tell application "System Events"
    		repeat until visible of process "Emacs" is true
    			delay 0.5
    		end repeat
    	end tell
    	return input
    end run

and the Shell Script part (pass input to stdin) is:

    tmp=$(mktemp "$HOME/tmp/EditTextinEmacsXXXXXXXX")
    ec=/Applications/MacPorts/EmacsMac.app/Contents/MacOS/bin/emacsclient
    cat > "$tmp"
    until [ $($ec -q -e '(server-running-p)' 2>/dev/null) == t ]; do
      sleep 1
    done
    $ec -q -c "$tmp"
    rv="$?"
    cat "$tmp"
    if [ $rv -ne 0 ]; then
      echo "Something went wrong.  Please find your text in"
      echo "$tmp"
    else
      rm "$tmp"
    fi

Getting it to work with any editor should be straightforward.