Hi Jeroen,
I don’t think you need to access the document.title of the history object. As far as I can tell from the Piwik documentation, you need to configure a history change trigger, which triggers every time the window.history object changes. Then, you can configure Piwik to retrieve the document.title after the history trigger goes off. document.title correctly returns the current page title on a Mendix page, so that should do the trick.