Foreman-debug tool automatically evaluates scripts in particular directory, which is used by other plugins. There is currently no way of putting a line onto the summary page. There was a downstream only patch that adds some info.

If there is a way to add lines onto the summary page, external plugin could do something like:

# cat /usr/share/foreman/script/foreman-debug.d/my_plugin

add_cmd "cat /usr/share/foreman/lib/satellite/version.rb" "satellite_version" 
SUMMARY += ("SATELLITE:", "$(grep -o '[0-9\.]*' /usr/share/foreman/lib/satellite/version.rb 2>/dev/null)")

This can be used for example in the Satellite branding plugin.