I run this script using an ssh key to create a file with the current IP of my machine. Change user@host.com to a user with ssh key pair on your machine. I then access this file from my server.

current_ip.sh

#!/usr/bin/env bash
# This script should only generate an email when the WAN IP has changed.
# run in launchd

#test for any parameter, true if debugging
test -n "$1" && dbg=$1 || dbg=false #;dbg=true

echo "Running $0"
my_ip=`curl -s http://checkip.dyndns.org | awk '{print $6}' | awk ' BEGIN { FS = "<" } { print $1 } '`

if [[ -s /tmp/prevIP.txt ]]; then
  prevIP=$(cat /tmp/prevIP.txt)
else 
  echo "initialize" > /tmp/prevIP.txt
  prevIP=$(cat /tmp/prevIP.txt)
fi

if [[ $my_ip != $prevIP ]]; then
  echo $my_ip > /tmp/prevIP.txt
  my_change=`echo $prevIP "-->" $my_ip`
  echo $my_change
  scp /tmp/prevIP.txt user@host.com:/tmp
fi


t=`date +%k`
t=`expr $t % 4`
if [[ $t = 0 ]]; then
  echo "sending current IP"
  scp /tmp/prevIP.txt user@host.com:/tmp
fi

if [[ $debug == true ]]; then
  echo "===="
  echo `cat /tmp/prevIP.txt` 
  echo $t
  echo "===="
  rm /tmp/prevIP.txt
fi