http://doc.qt.nokia.com/qtcreator-snapshot/creator-mobile-example.html there is text

2. Include the System Info header file, as illustrated by the following code snippet:

 #include <QSystemInfo>

If one follows these instructions, the example won't compile - the pointer later in .h is QSystemDeviceInfo* and one gets an error

BatteryIndicator/mainwindow.h:40: error: ISO C++ forbids declaration of 'QSystemDeviceInfo' with no type

One should include instead a different header, QSystemDeviceInfo. With such include the example compiles and runs as described in this docs page.

I attach a patch (to docs and example code) against the newest git version of 2.1 branch.