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.]
Piwik Analytics Plugin for xt:Commerce released
Today the first version of the Piwik plugin for xt:Commerce has been released. The plugin dynamically integrates the Piwik Ecommerce Tracking Code on all websites of a xt:Commerce shop.
In contrast to other plugins the current Piwik code is used. The current code is loaded asynchronously and therefore does not slow down the page generation.
All further information about this plugin can be found here.