Thanks @yvesago!

I tried to sign up with https://spur.us to get an API key and test your code in action. However, I understand

1. it's possible to sign up only with a company email
2. to get an API key I need to pay $125 per month, there's no free plan

Did I get that right?

Your are right, free webmail are not allowed and there's no API free plan.
But you have all API results in web console search with free plan.

Ok. In that case I'm not sure it's worth adding to checkip because I guess I won't be used but the code will have to be maintained .... What do you think?

I will use it daily ;-)
I can maintain the code. And I will keep it as minimal as your wrote other checks. I like your code.