Ok, I think I get it now...
So the way Movies work is that they all open up in a new browser window, and depending on how your system/viewers are configured, they may be displayed in your browser, in the viewer, as a "open/save" dialogue box, etc...
To be honest, having the script check to see what viewers are installed is scary. What works on a PC won't on a Mac, and I'd also be invoking Java access warnings (probably).
I think the best route is to just serve up the video, and let the viewer that's configured for that format handle it the way it wants to.
Kind of leaves things at the mercy of the user's config, but otherwise they get stuck with what the script wants...

As for embedding code, I'd like to be able to do that... It would allow things like Flash movies to be uploaded as well, which isn't currently possible... It's on the drawing board, but I'm trying hard to clean off the V6 to do list so I can get it out the door...