To me that looks like a mistake by the Verelo programmer, in interpreting the "over limit" response from your API as being "down". To term that a "scam" is an equally misleading. I don't believe it is fair that you cast aspersions without proof. "Publicly shaming" you is a wild accusation.

If I had put such a service together, I can imagine that I would search for a public API method that I could call, and if I received a response I would assume that the API was up, and vice-versa. The developer has mistakenly interpreted an error response code in the context of a user over access limits as an entire API failure. An automated script keeps running and gives incorrect results. That's an oversight and not a scam.

I think you would have been better to try to get an explanation from Verelo before publicly shaming them. They might have worked with you to correct the problem.

By the looks of the http://whatsdown.verelo.com/ website, the vast majority of the sites appear to have valid uptimes. Yours is the primary exception. That suggests to me that this truly was an oversight, otherwise they would have been trying to extort other services in the same way.

Contact Verelo, and ask them for an explanation. If the explanation is valid and they correct the error, then I think they deserve a public apology from yourself.

On a side note, it might be useful for all public APIs to offer a standard /status call, which returns a standard response. In that way, services like these, which do have some value, could operate in a standard way without upsetting the API owner.