ProcessWire Auto Sitemap Submit Module
This module hooks into the Publish and Save page events. If a page is published or a page that is published has been saved this module will ping Google and Bing with the updated sitemap.xml file.
The module will check if sitemap.xml exists. All submissions/failures are logged and accessible via Setup->Logs->auto-sitemap-submit
If a page is saved or published and sitemap.xml is not found, a warning message will appear notifying you that the sitemap was not submitted.
Ain't no fancy configurations or nothin', just make sure you have a sitemap.xml file and you're good to go.
Recommended companion module: MarkupSitemapXML