Two OpenID plugins Rated 4 out of 5 stars

Would be good to unify this with the existing Firefox OpenID plugin somehow:

https://addons.mozilla.org/en-US/firefox/addon/openid-login/

Allowing web-sites to query your preferred OpenID sounds like a privacy risk, though.

This review is for a previous version of the add-on (1.0.4). 

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.