I have not started this yet, as I have been sick with pollen…
However, when I investigated the size of a project like this, I saw that it should not be that complex to implement this as a plugin. I will start sometime after the summer I think.
I have created a first draft/concept of this, if you want to experiment. :)
You then need to implement the function `processResponse’, and maybe something more, IDK.

https://github.com/sebastiw/PollenCountForMagicMirror