Two OpenID plugins Rated 4 out of 5 stars
Would be good to unify this with the existing Firefox OpenID plugin somehow:
Allowing web-sites to query your preferred OpenID sounds like a privacy risk, though.
I sent an email to info (at) it-innovation.soton.ac.uk but did not get a reply. Yes, let's talk about joining forces.
Regarding the API the addon is providing: This is implemented like the W3C geolocation API. The preferred openid is only provided to the web-site after the user has given their consent.