be warned via xmpp every time a user logs in you linux machine

gistfile1.sh

#you'll need xsend.py script from http://xmpppy.sourceforge.net/examples/xsend.py . it's easy enough to get the dependencies

#/etc/pam.d/sshd
session optional pam_exec.so seteuid /home/YOURUSER/sshlogincmd.sh

#~/sshlogincmd.sh

#!/bin/bash
if [ $PAM_TYPE  = "open_session" ]; then
        /usr/bin/python /home/YOURUSER/xsend/xsend.py youxmmpuser@example.com user $PAM_USER \($PAM_RHOST\) $PAM_TYPE logged in on $HOSTNAME &
fi
$SSH_ORIGINAL_COMMAND