Ready Now

Any service, big or small (consider Craigslist.org, for example) could do any of these today:

This (and only this) is what the Nerdster and the ONE-OF-US.NET phone app use. The phone app stores your identity private key on your phone, and Nerdster can remember your private delegate key, but otherwise, both apps read and verify your own signed, published content as they load up just like other services would to leverage that data.

QR Sign-in

There is no special access between one-of-us.net and nerdster.org. The ONE-OF-US.NET phone app reads the Sign-in Parameters in the QR code, checks if a delegate key for ("domain") is present, and then performs an HTTP POST over the Internet to the address ("url") it was instructed to, optionally end-to-end encrypted using the disposable encryption public key provided ("encryptionPk").

Our signed content is published

For example: My signed content is here: identity, Nerdster content.
Both services publish all signed content at https://export.<service>/?spec=<key token>.

Services are free to choose

Other services don't need to be as naked and transparent as the Nerdster, don't have to use delegate keys (just identifying a Point of View (PoV) might be enough), and they don't have to expose folks' signed content, although this enables other services to audit, and that can enhance credibility, which is nice.