iPhone登录Google App Engine

Is there any way to log into a Google account from inside an iPhone application if you know the username and password of the account. I want to be able to do this without making the user type in the information each time the app has to login. I need to do this so I can have a login system accessable from the iPhone SDK. Actually any login system will do if it can run on the app engine.Is there any way to log into a Google account f