I attached an example.
It has some boilerplate code from the SDK, so it may look a bit more complex.

Also I use dbus-send and gconf inside a QProcess, because I think it is much easier than using dbus / gconf bindings inside Qt for such simple tasks.

If anybody has a simpler way, or a cleaner way using the dbus and gconf bindings, please share

The example is just a button, that does nothing. But you will notice that the touchscreen sounds and touchscreen vibration feedback are automatically disabled when the application has focus (when the application window is "active" to use the correct terminology), and are re-enabled when it loses focus.

any comments/improvements about the code: please share