To add sitemap to your module you need to add a record to 'sys_objects_site_maps' table and custom class:
id - autoincremented id for internal usage
object - your unique module name, with vendor prefix, lowercase and spaces are underscored
priority - priority, allowed values from 0.0 to 1.0
changefreq - how frequently contents change, allowed values: always, hourly, daily, weekly, monthly, yearly, never
class_name - your custom class name
class_file - file where your class_name is stored
order - order in which this sitemap is generated
active - is object active, allowed values 0 or 1
You can refer to BoonEx modules for sample record in this table.