I had this idea long ago and posted a topic even with some concepts i was thinking about on how to do it.
but as far as i know it was not done by anyone
i wanted people to use their Wifi or ethernet hardware for Proof of work basically.
and i wanted to incorporate file sharing as the actual work.
i started working on eMule mods back in like 2004'ish so i am familiar with P2P code
and i envisioned the quickest way to do it would be to port the credit system from eMule sort of.
but all of this would be a lot of work though and sadly i am lazy and always have too many projects on the go half finished.
the File Sharing angle i ithought might be controversial to some people though..