To Install System Status:

(these steps worked for me using a KDE4 desktop on gentoo)

tar -jxf /path/to/system_status-version.tar.gz
cd system_status
mkdir build
cd build
cmake ../ -DCMAKE_INSTALL_PREFIX=/path/to/kde4
make
sudo make install

then run
kquitapp plasma && plasma

The applet should appear in the add applets dialog.
