In my brain this seems simple. Simply search the site for a text link that says "next" and autoload the page for that link. If no "next" exists, check to see if the page number can be increased sequentially. If neither of those exist, allow the user to designate what the "next" button looks like, weither it be an image (which the app could then search the next page for),
or a different word (ditto),
or even a location on the page that stays the same (ditto again).
The app (at least for me) could be a way to read through a lot of webcomic archives without a lot of stress. It could keep track of where you are in the archives, provide the (seemingly required) post to Twitter, email, or Facebook buttons. It might even have a public catalogue of webcomics that the user could add to as they read the comics. (Maybe with tags, descriptions, whatever else).Just a thought.