not sure what newsgator is, but "Feeds" is a really nice app and is only 0.99
Go here...
http://www.newsgator.com/Individuals/Default.aspx
Essentially, for my laptops and desktops, I have FeedDemon installed to view all my RSS feeds which is sync'd with Newsgator.
So if I read all the feeds on my laptop and then decide to go to my desktop, it will know all the feeds that I have read, marked to read later, flagged, etc. etc. etc.
NetNewsGator for the iPhone is an app that is also sync'd with NewsGator. So if i read all the feeds on my iPhone, when I get to my desktop/laptop, it will know what I have read already...