In developing a mobile application that uses OpenID for logins one of the things I've become really cognizant of is how poor of the mobile experience most Providers have when it comes to OpenID. It obviously doesn't take a lot to create a streamlined Provider flow for authentication and the trust request, but so far it seems that no one has really done that. I was also thinking more about Providers such as YubiKey where authenticating with a USB device (despite how awesome it is) won't work on my iPhone.

I'm wondering if it would be useful to write a dead simple extension to provide some hints around mobile support? Allow a Provider to advertise in an XRDS file that they support a mobile login flow so that Relying Parties could discover that theoretically making it so that I could use a Provider such as YubiKey on the desktop and then MyOpenID on the phone.

Am I barking up a useful tree? If I spec'd this would any Providers actually implement a mobile friendly flow?

--David