However many useful classes and methods hidden by Google and manufacture, and developers be restricted to implement more advanced function.
For instance, the Bluetooth API was disclosed at Android 2.3, but it's available at Android 2.2 already. And the "android.randerscript" package for 3D calculation was disclosed at Android 3.0, but it's existed at Android 2.3 already.
Google list 3112 classes at API document, but this tool found 9082 classes at Galaxy Nexus. In other words, more than 5000 classes were hidden by Google, and those classes may be the key point to help developer to implement advance function.
Try to discover more useful classes and method at your Android device, it may help you to make more miraculous function at your application.
You can download this tool at URL below.