Jernbaneverket provided this solution for us! The announcement is here, Monitorvisning i nettleseren. The registration form is here, you have option for English in top-right corner.

After registration, you could create your own monitor, please choose a station, Departure or Arrival, and how many rows. After click “Save”, try to “Show” it, then you got the url for this monitor, for example, my “Oslo S-Departure” monitor is http://rtd.jbv.no/rt/display/faf2d9be57ae94ce548ebfd61e26f61a45e487e3.

For Mac users, launch Safari, open the above url, adjust the display windows, then click “File”->”Open in Dashboard”, select the area which you want to show in the Dashboard, then click “Add” button in top-right corner of Safari.