I have tried to write an Android application with an activity that should be launched from a different application. It is not a content provider, just an app with a gui that should not be listed among the installed applications. I have tried the code examples [here](http://www.damonkohler.com/2009/02/android-recipes.html) and it seems to be quite easy to launch existing providers and so on, but I fail to figure out how to just write a "hidden" app and launch it from a different one.

The basic use case is: 

* App A is a normal apk launchable from the application list.
* App B is a different apk with known package and activity names, but is is not visible or launchable from the application list.
* App A launches app B using the package and class names (or perhaps a URI constructed from these?).

I fail in the third step. Is it possible to do this?