Since my IP hardly changes, I went from DDNS to an email notifying me when the IP changes with this cron:

  old_ip=`cat ~/.prev_ip`
  my_ip=`ifconfig em0 | awk '/inet/ {print $2}' 2>&1`
  my_email=me@example.com

  if [ "$my_ip" != "$old_ip" ]; then
    echo $my_ip > ~/.prev_ip
    echo $my_ip | mail -r $my_email -s "New IP: $my_ip" $my_email
  fi