simtoolsgui provides two basic features, the notion of a ProbeDisplay and a kind of graphical Swarm called a GUISwarm.
ProbeDisplay
ProbeDisplays present an object's variables and messages according to a ProbeMap. ProbeDisplays are the graphical means by which the user controls VarProbes and MessageProbes associated with a given object.
GUISwarm
A GUISwarm is a kind of Swarm that is used in most simulations as a kind of observation wrapper around a model. It provides a control panel to start and stop the model along with any activities for updating observation widgets in the simulation (e.g. space library objects, probe displays).