The Piwik tracking code integration plugin has been published in the official xt:Commerce plugin store and can be downloaded from there: http://addons.xt-commerce.com/en/Plugins/Statistic-/-Tracking/Piwik-Analytics-Ecommerce-Tracking.html [Update: the plugin has not been tested/updated for xt:Commerce 5/6, thus it is currently not available in the official plugin store.]