Johan, a lot of it is very experimental, but is roughly supported by WordPress. I’ll take a look at that page and see if I can flesh it out with a few more examples (including parts of mine) as I think there are some hiding out in the wild besides mine. There’s at least one other version I’m aware of that hasn’t been documented either.
I suspect you could take one of the Known community plugins and modify it to create follow posts on Known to send follows to others’ sites. I’m not quite sure how you’d display follows to the public on your own site, though I do know that Known core has part of an unfinished feed reader built into it with some following functionality already there. You can see some of it on your site (private, I think) at