Plex is a wonderful tool for media viewing, categorizing, etc. and I think it would be great to join that with Alfred. I know Plex has an api though I don't know enough about it to get the job done myself. I was thinking at first it would be awesome to be able to just search through the media server from within Alfred (perhaps being able to hit enter on a title and it launch the web version of plex). Something that it could technically also due based on a glance at the API is actually controlling a remote plex media center, which would be awesome.
What do you guys think?