Is there a way to give oEmbed codes a special markup in the visual editor? In my dream implementation you paste an oEmbed-enabled url in the editor, which will then automatically replace it with a thumbnail of the media object you want to insert. A basic implementation would at least highlight the URL so the user knows "something special" could happen there (if no errors occur).
Is there a plugin that does this? I could create something like this myself, but I would need some pointers on how to hook into the TinyMCE editor in the most WordPress-stylish way.