Feed Filter changes the feed content based on consumer's IP (so you can send bad content to content thieves).
Feed Filter can be configure to manipulate the feed served to some specific IP addresses. I used it to send reduced content with no images, back links and copyright notices to automated blog network that was republishing my contents.
More, the plugin can "delay" the feed seen by specific IP: this is useful to have you article titles published before sites or networks that republish (legally or not) your feed items.
I wait for users comments on http://www.satollo.net/plugins/feed-filter.