Install:

1 - copy the plugin to folder plugins;

2 - install the plugin inside pwiki admin panel;

Notes:

this will create 2 new tables "custom_stats_category" and "custom_stats_log"

• custom_stats_category: the custom category name and field names
• custom_stats_log: the custom tracked data relative to the category
  The categories must by created manually.

Tracking:

piwikTracker.setCustomData({
'MyCustomData': { //used for avoid conflicts with anothers plugins
'CustomUserTrack' : {//the category name saved in custom_stats_category
'id': '1', // label: value, the custom tracked data itself
'name': 'Diego', // label: value, more custom data
}
}

});

Actually this only saves the data, but don't show the data in the panel, i hope someone can continue this plugin.

(Sorry for the bad English)
Keywords: custom data track