I would like to see something like this too. I've been reading up on HTML 5 video and it seems the standard methodmis not too difficult but it requires 3 different video formats. The usual mp4, another for FF then the Flash fallback. Apparently, ll grail video has this covered, and I've heard if a new on called pickle player that supposedly only requires one video file format to work for everything.
The problem with any of these is the implementation, it's often harder than they let on. And rarely do I like any of the skins and control bars. In extesnsion form, it would be great.
Same goes for photomgalleries. Plenty of options, hard to implement. Compare those to Wordpress plugins, such as next gen gallery, which is free and offers all sorts of viewing options asmwell and uploadingnandnasset management, all part of the plug in.