I can give you a bit of an overview of LG Better Meta in regards to the sitemap functionality.
LG Better Meta allows you to add per entry meta including priority and change frequency. You can also assign defaults for these values on a per weblog basis.
The sitemap generator automatically creates a sitemap file for you and pings the major sitemaps. Ben will be able to tell you more how the urls are constructed.
LG Better Meta gives you the ability to create completley unique urls for your sitemap file which is created as an EE template using the following code:
<?xml version="1.0" encoding="UTF-8"?>
<urlset >
{exp:lg_better_meta_pi:entries
weblog="blog"
disable="categories|custom_fields|category_fields|customer_fields|member_data|pagination|trackbacks"
dynamic="off"
rdf="off"
status="not closed"
}
<url>
<loc>http://test.com/blog/post/{entry_id}/{url_title}/</loc>
<lastmod>{edit_date format="%Y-%m-%d"}</lastmod>
<changefreq>{change_frequency}</changefreq>
{priority}</priority>
</url>
{/exp:lg_better_meta_pi:entries}
</urlset>
If you want to ping a server everytime an entry is published you can use EE’s inbuilt functionality for this.
If you want to add custom pages to the generated sitemap you can just add them to the template.
Hope that helps