[rahoulb]

Add in an "auth-request" header onto the email, have a plugin for your mail client that looks for the header - and if found hides the mail and does the auth in the background for you - and you then have seamless integration (thanks to http://news.ycombinator.com/user?id=wlll)

[BoppreH]

Enter page, type email, hit enter, wait 5-10 seconds, "You are logged in."

Apparently simple to implement for both customer and provider and takes alway all the headaches from account registering.

I would pay for that.