I do not know what the OP intentions are, but I find a need to use both DNS service and a need to know my extrenal IP.
So I do use N0-IP.com, but also use the WWIP software that emails me to a Gmail account the IP and I can log from any where in the world and know my IP.
As an example, it is much easier to do Remote Control with VNC if you know the IP.
There are few applications that can read the external IP and email them or post them somewhere of your choice, but all of them have to log to an external sources to find the IP.
WWIP is the only one that I found that does not go out, it reads the IP from the firmware of the Router.