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PiwikCounter is a Counter which needs a Piwik installation under your control. Without it, it won’t work. 
It get’s its data through Piwiks API and caches the amount of visits until yesterday and just adds the amount of visits for the actual date.

PiwikCounter

PiwikCounter allows you to show the summary of (unique) visitors as a widget on your blog.

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 (https://wordpress.org/extend/plugins/twitter-tools/) and does not work without it.

Twitter Tools – Piwik Campaign Tagger

This plugin adds a "piwik_campaign=twitter" to the URL that is published by Twitter-Tools and then shortens it using bit.ly.

PiwikCounter vs Twitter Tools – Piwik Campaign Tagger