From that link -
<!-- MPlayer will follow me around when i switch desktop.
that way i can always watch my vids when coding.
same goes for Realplayer -->
<application class="MPlayer">
<desktop>all</desktop>
<layer>above</layer>
</application>
<application class="Realplay.bin">
<desktop>all</desktop>
<layer>above</layer>
</application>
Couldn't set up mplayer and realplayer together, So it looks like apps need to be set up individually.