This is really great news! This have been a dream for a long time. Now we have an OpenIdP that you can connect to without any metadata exchange!
The latest version of simpleSAMLphp (from trunk) is also preconfigured to trust the OpenIdP. You can now download simpleSAMLphp and then without modifying a single line of configuration, or exchanging metadata with anyone, you can perform a login through the Feide RnD OpenIdP.
The default behaviour of simpleSAMLphp as an SP would be to set the entityId equal to a endpoint at your server that automatically generate hosted metadata for your service. Then OpenIdP supports looking up metadata on that URL and uses it.
Next step with OpenIdP would be to enable user consent, which means users will have more control of which services that retrieves information about your Feide RnD OpenIdP identity.