IMPORTANT: The "ping" sitemap endpoint has been deprecated by Google
You can submit your Sitemap URLs to Google completely for free from this simple tool.
This tool runs from your browser, so it's 100% private. The requests are sent from your browser to Google's API. Nothing goes through this website's servers.
Consider that this endpoint is supposedly only accepting XML sitemaps, but you can try to send normal URLs, it is not limited in any way.