First answer: No.
Second answer: Maybe.
Marked is a markdown previewer. Instead of being the editor, it watches the file you are working on, and updates whenever it changes. Presumably this is quite nice if you are using an editor which auto-saves. It claims that the easiest way to get your document into Marked is to drag the icon from the toolbar. Unfortunately, this doesn’t work with Emacs, as there is nothing to drag.
I’m trying out Marked while writing this post. Octopress’s document format is markdown, which is primarily why I care in the first place. Editing README.md files that will render on github is another reason why I might care.
Marked can be tweaked to match your actual use case. For example, at the moment, I need line breaks to not be preserved, as I know that octopress won’t preserve them, yet Emacs is adding them. Additionally, you can instruct Marked to ignore YAML front-matter, which octopress also uses, and is a bit distracting to see in the preview.
Since I seem to frequently produce Marked documents with formatting flaws (how do I create a code block, again?), this tool might find its way into my workflow.