kasperbs,
I know it’s been 5 months ago, but how has your work progressed? I have used postTabs plugin which functions satisfactory for my implementation – a Post with faux sub-pages under tabs. Although, from the beginning, I was searching for something found for example in the WordPress Plugin Directory, where the tabs go to the actual sub-page permalink.
I am going to try and implement tabs directly in the Single.php-template of WP by for example querying the child pages of the current Post and then inserting them into inline tabs using only css and perhaps a little javascript. What do you think?