How to find out your extrernal IP from Linux

This question has troubled me as I want to create a script which will email me when my router address change. So since I always have a computer on, I thought that I could check the external IP and send me an email :)
The solution for the IP is found here

The command is:

curl -s checkip.dyndns.org|sed -e 's/.*Current IP Address: //' -e 's/<.*$//'

When I create (maybe after many months) the whole solution for the idea, I'll post it here.

Cya!