android-2.2

Is Android "open" enough to let you disable built-in features such as Phone book etc?

Hi, Is it possible in Android, to disable standard features of the phone such as Mail, browser, phone etc? What I'm asking is, is it possible to create an application that, when launched on startup provides some features to the user, but sits "on top" of android so they only have access to your application and not the underlying featur...