Currently the only stuff that will play is what you can play using Windows Media Player - no RealPlayer stuff
I had the same issue with internet radio feeds. In the end I had to set up a media server that translated the feeds to something else. For RealAudio that was SlimServer. It outputs the feeds as MP3 using the AlienBBC plugin for it. As for video though, not sure if there is something similar. I think that would be your only way to do it though.