put this in your .zshrc

case "$STY" in
  "")
    ;;
  "$PPID".*)
    precmd () {
            let "len = 54 - ${#DISPLAY}"
            screen -X -S "$PPID" title "$DISPLAY - `pwd|sed -e 's:^.*\(.\{'$len'\}\)$:..\1:g'` ($_my_last_cmd)"
    }
    preexec () {
            screen -X -S "$PPID" title "$DISPLAY - running: $1"
            _my_last_cmd="$1"
            # # Maybe $2 or $3 is a better choice - I didn't get the difference yet. You may
            # # analyse this with the statement:
            # printf "1:%s\n2:%s\n3:%s\n" "$1" "$2" "$3" >> "/tmp/preexec.$$.log"
    }
    ;;
esac

On Mac OS X (maybe on BSD systems in general), screen launches a login process which then executes the shell. Therefore, the id of the screen session ($STY) does not start with the parent processes pid ($PPID), but with the parent pid of the parent process. Therefor, you have to use the following lines in your .zshrc

case "`ps -o 'command=' -p $PPID`" in
"login"*"zsh") pppid="`ps -o 'ppid=' -p $PPID|sed -e 's/^ *//g'`" ;;
*)        pppid="XXX" ;;
esac

case "$STY" in
  "")
    ;;
  "$pppid"*)
    eval " 
    precmd () {
            let \"len = 54 - \$#DISPLAY\"
          screen -X -S "$STY" title \"\$DISPLAY - \`pwd|sed -e 's:^.*\(.\{'\$len'\}\)\$:..\1:g'\`\"
    }
    preexec () {
            screen -X -S \"$STY\" title \"\$DISPLAY - running: \$1\"
    }
"
    ;;
esac

This is the beginning of an humble try:

case "$STY" in
  "")
    ;;
  "$PPID".*)
    precmd () {
            let "len = 54 - ${#DISPLAY}"
            screen -X -S "$PPID" title "$DISPLAY - `pwd|sed -e 's:^.*\(.\{'$len'\}\)$:..\1:g'`"
    }
    preexec () {
            screen -X -S "$PPID" title "$DISPLAY - running: $1"
            # # Maybe $2 or $3 is a better choice - I didn't get the difference yet. You may
            # # analyse this with the statement:
            # printf "1:%s\n2:%s\n3:%s\n" "$1" "$2" "$3" >> "/tmp/preexec.$$.log"
    }
    if [ "$BASH" ]
    then
      PROMPT_COMMAND='precmd'
      screentitle() { preexec "$BASH_COMMAND"; }
      # # nice try :-/
      # trap screentitle DEBUG
      on_debug()
      {
        case "$BASH_COMMAND" in
        "$PROMPT_COMMAND") ;;
        *) preexec "$BASH_COMMAND" >> /dev/tty < /dev/null 2>&1 & disown ;;
        esac
      }
      trap on_debug DEBUG
    fi
    # as we show user and cwd in screen title, 
    # clear hardstatus in screen:
    echo -en "\033]0;\007"
    ;;
esac

This seems to break some Pipe chains. There might be a better approach at at twistedmatrix where the idea to use ”trap … DEBUG” was stolen from

Actually, I consider this trick dirty and hence both solutions.

#remove some stupid / dangerous key bindings
bind ^k
bind ^\
bind k
# # don't lock screen accidently - use if you don't know the accounts password (e.g. when access is managed by ssh keys)
# bind x
# bind ^x
startup_message off
vbell on
vbell_msg " Klingeling! "
bindkey -k kb stuff ^?
defscrollback 500

caption always
# # show window title and optional
# # hardware status line text
# caption string "%?%F%{.c.}%?%3n %t%? [%h]%?"
# windowlist string  "%3n %t %?[%h]%?"

# show window title if set, 
# else hardware status line text
windowlist string "%3n %?[%h]%:%t%?"
# show clock in caption line
caption    string "%?%F%{.c.}%?%3n%? [%h]%: %t%?%=| %c:%s "

hardstatus on
hardstatus alwayslastline
msgminwait 0