I'm giving a go at something like that, was wondering if there was similar stuff out there

cheers

I've got an example of one somewhere on the list.

But it's Purr Data only because it uses an svg-style affine transformation (rotate) which greatly simplifies the patch.

You could check gridknob I uploaded a while ago. Near the end of this thread https://forum.pdpatchrepo.info/topic/10838/no-mouse-external-some-success
Cheers
Balwyn