Fookb is Xkb state indicator. It can display an icon corresponding to current locked Xkb group. It also can switch Xkb groups.
Fookb is primarily designed for WindowMaker window manager so it can be compiled as a dockable application with libWUtil (prior to 3.0 libPropList) support (hence should be configured with ~/GNUStep/Defaults/FOOkb file).
But if you do not have WindowMaker and/or libProplist/libWUtil fookb will work too. You absolutely need libX11 and libXpm. Without WindowMaker fookb will work as usual X11 application. Without libWUtil/libProplist fookb should be configured with X resources and/or command line parameters.