This plugin helps integrate your blogs twittering into Piwik (
http://www.piwik.org) more tightly. Whenever you post a blog entry and Twitter Tools tweets your post, this plugin will add a "piwik_campaign=twitter" to your post's url and then shorten it. This way, you can keep track better of the visits that come to your site following your tweets.
This plugin builds on Alex King's Twitter-Tools plugin (
http://wordpress.org/extend/plugins/twitter-tools/) and does not work without it.