I love the fact that you've made this plugin extensible through the custom modules API. However, I'm not sure if that's the best way to go about accomplishing what I'm looking to accomplish.
I have another plugin that creates a large amount of custom data and outputs it through WordPress. Within that plugin, an XML sitemap is generated for each entry within that custom data. I would like to simply add a line to the sitemapindex file (or even the page.xml file if that might be easier) that points to the custom sitemap that's being generated by that plugin.
Basically, to give you a little background; we have a custom plugin that pulls in ~400 entries from an external source, then parses that data into a format that can be output in WordPress. The plugin then combines data from within the WordPress database with the data that was pulled in from the external source, and creates a new virtual page for each entry. Those virtual pages are not stored as content entries within the WordPress database, as they can change on a daily basis (one may disappear, a new one may be added; it's all controlled by the data that's retrieved from the external resource).
Since all of those entries are virtual, the plugin itself generates a sitemap of all of the entries that are generated. I simply want to add a link that leads to that custom sitemap within our sitemapindex file, so I don't have to go through all ~250 of our sites and manually submit the custom sitemap to Google.
Is it possible to simply add a new entry to the sitemapindex file without having to write an entirely new module within the API? Or will I have to write a custom module that somehow hooks into the methods that are already written to generate that custom sitemap? Thanks.