Android :: Good Way To Register Users From Phone Application

We have a web application and we've built phone applications (iPhone, Android, BlackBerry) to be companions to the site. The usual workflow is that an existing user of the site gets a phone app and then plugs their existing credentials into the phone app and they are off and running, but more often now we are seeing folks who are downloading the app and then (and this should not surprise anyone) don't read the help screen that explains they need to go and get credentials at the web site and therefore cannot connect to the application which does require registration to manage their content. This is a giant usability fail condition.

So we know that we need to put user registration workflows on the phone app. Other than the obvious solution of duplicating our registration page on the mobile, does anyone know of a better identity solution for the phone? For example, on the desktop we also use Facebook Connect as an identity server and the users love it. I'm looking for something that simple that we can implement across the major smartphone platforms.
Clarifying note: I should add here that this registration mechanism is likely to; and it would be desirable if it did, go hand in hand with a general identity/authorization mechanism such as the Facebook mechanism mentioned below. One other place I'm poking around is to see whether there's an openId solution that does not require a browser to pop up.