What's the best way to tie a mobile app user to their online profile?

Let's say I have a killer mobile app named X. I have lots of users and some users want a desktop version of开发者_如何学运维 X. How do I associate my mobile users profile with their new website profile? I don't want to have a username/password on the mobile device, because all of my users are on mobile and have a unique mobile device id already. I was thinking about generating a short UUID in the cloud, send it to the device and when the user signs up for the website they just input their UUID and email. Is that the best way to do it? Is there a better way?

Integrate with Google's auth. The phone will pop up and ask you which (of all the Google accounts you associate with your phone) you want to use. Then you website and/or other apps need to be able to handle Google's sign-in.

Try something like OpenID, where in you have one Id which can be associated to multiple devices as it would be user specific and there will not be any issue as such.

For example, we have something like SO has implemented on it login page.

By using the user's unique device ID, you potentially limit the user to a single mobile device. (What happens when the user gets a new phone/tablet?) If you are providing a service across multiple platforms, (e.g. mobile, desktop, and web,) I don't think it would be outlandish to require a username and password.

Another option would be to leverage another platform that already does authentication, such as Facebook Connect, or OpenFeint. Of course, it should simply be an option: users shouldn't be required to have such an account to use your service.