The following lines I put into my .zshrc might not be very pretty, but it is short, seems to work and I don't need to use any of graphical tools to ssh somewhere with my key (with passphrase). So it works fine with my zshell and E17.
SSHPID=`ps ax|grep -c "[s]sh-agent"`
if (( $SSHPID == 0 ))
ssh-agent > ~/.ssh-env