Does that mean GoSquared will report a page that has been open for days, taking up a tab but not being actively looked at, as 'online', or is there a timeout after a specific period of inactivity?
I don't know about GoSquared, but I built a similar real-time dashboard for W3Counter [1] that operates the same way. It would include that visitor as long as the tab is still open, but it also shows how many visitors are idle versus writing or reading (recently scrolled or moved the mouse, which requires the tab be in the foreground), so you know how many are just sitting in tabs.