Currently, the XBL bindings that we have made available allow for streaming video to be implemented in output via two players: Real Player and Windows Media Player.
To use them, simply put the URL of the stream in to the value attribute (this can be the result of an XPath expression if you like) and add an appropriate mediatype attribute ('audio/x-pn-realaudio-plugin' for Real Player and 'application/x-mplayer2' for Windows Media Player).
For example:
<xf:output value="'mystream.ram'" mediatype="audio/x-pn-realaudio-plugin" />