I know it is possible to sent OpenURL requests to the WorldCat Registry
service and have it chose a local OpenURL resolver based on what IP address
you are coming from.

WorldCat OpenURL endpoint: http://worldcat.org/registry/gateway

What I don't know is if WorldCat has an OpenURL resolver or can itself act
as an endpoint for an OpenURL? I realize this is not the usual use case;
normally an OpenURL would be searching against a knowledgebase of the
holdings of a specific institution. With WorldCat, the OpenURL would have
the holdings of all the constituent member libraries as its "knowledgebase".
So, the purpose of this would be to discover where a given item represented
by the OpenURL was held. A secondary purpose would be as a source of
bibliographic citation information This could be quite useful discovery
tool, especially for materials that are not widely held.

Ditto the same question for OpenLibrary.

Tom