FWIW, I built something like this for myself years ago because I needed to know when my ip changed. I locked it down so I'd be the only one able to use it. When I first saw jsonip.com, I kicked myself.

The brilliance of jsonip.com isn't really the service, it's the vision that it should be free and world-readable.

I saw your project on reddit - really nicely done. But I can't think of a way to monetize it either.

Maybe make a landing page with some ads?