iFinity

It is not currently available as a download.  The property agent provider is part of a larger portion of work I plan to do on sitemap providers, but for now, it's not available.  I will announce a release of it if this changes.

Not at all.  A sitemap is just a list of 'hints' for search engine robots to find content on your site.  It isn't binding.  Omitting urls from the pages does not necessarily mean they will not be indexed : links from your other pages will be followed, and this will include some of the property agent links.  Perhaps you might not get complete coverage from a search engine of all the items, but any important/popular items are likely to be indexed.