MaemoN00B: Your method, once I understood how the whole "hildon-" thing works, gets me part of the way there. I made a usr/share/applications/hildon/mplayer-CLI.desktop file for mplayer, referred to it in that file you mention, and I get "CLI MPlayer - loading" in the top right of my screen, but that's all.

I think, as pipeline says, hildon apps simply do not pass filenames to the associated apps except through this dbus system, so that rules out command-line apps like mplayer.

Does this maemo kmplayer app use dbus?

Interesting update: My attempt only got that far as long as I had an X-Osso-Service line in my mplayer-CLI.desktop file, and that method, as we have determined, is a no-go for non-hildon apps. As soon as I removed the X-Osso-Service line, file manager just throws up its hands and doesn't know what to do with video at all.