The DataCheckPanel is intended to be used for debugging purposes for the packager, not for inclusion in a final installer.
It creates a list of all the variables in InstallData, their values and a list of all packs, indicating which are selected. This list is printed to the console and appears in a scrollable text area on the panel.
Put the panel in wherever you want to see any variables in InstallData or a listing of the packs with a line like this in the <panels> section of install.xml:
<panel classname="DataCheckPanel" />
It will automatically give you a full list of all the variables and packs whenever the panel is made active.