Sencha-touch : save login / password (save session, multi-tasks)

I guess you already use a webservice somewhere to store/check the username/password combinations. When a login is successfull, you should create a Session Token on the server and return that to your app. Your app should store the token in the localstorage, together with your username and password and whenever you make any requests to your webservice, you should send your token along for validation. When you open your app for the second time, if the session is alive you can continue using the token. If the session on the server has ended and the server returns a token error to your app, you should resend your logininfo to the webservice to create a new token.

You can embed your Sencha Touch code into a UIWebView: http://developer.apple.com/library/ios/#documentation/uikit/reference/UIWebView_Class/Reference/Reference.html

This will allow your applcation to save state (i.e. not reload) if you exit and return to your application.