Using piwik to track embedded widget use

Hi,

I develop a WordPress plugin and want to use Piwik to track the use of that plugin. I included a tracking image with my plugin but it seems that no data is coming in. Is there anything I need to do to enable such use? Does the fact that I enter a website URL in the settings suggest that all requests to other site will be ignored?

Any help would be much appreciated.

Thanks,
-Gezim