Best OpenID Provider for iPhone / Mobile Device

Is there an OpenID provider that is really exemplary for use on an iPhone or other mobile devices?

Before you say this belongs on meta.stackoverflow.com, hold on, I promise this is a programming question.

If designing a highly mobile site, it would be nice to offer a large button linking to them from a login page (like the Google link gets a large button on Stack Overflow) so that it would be easy to hit them with a fat finger and log in quickly.

What would make a good mobile device OpenID provider?

• When you are redirected, the provider has a specific mobile-savvy login interface. You shouldn't have to pinch-zoom your iPhone just so you can select the username or password box.
  


• The provider should offer to remember you for a good long while so you don't have to keep typing in a complex password each time you visit.
  


• Login (and possibly even sign-up) should be as few screens as possible. There should only ever be one page displayed from the provider before redirecting back to the relying party's site.
  


• I would welcome comments that offer more "mobile-friendly" requirements, especially for Blackberry or other platforms as my experience is obviously coming from the iPhone.
  

Source: Tips4all