Custom page html headings plugin?

You could use a simple custom field and have it displayed on the page template.
Assuming you name the custom field “page-heading” this could help you:

<?php query_posts(); ?>
<?php if(get_post_meta($post->ID, 'page-heading', true)): ?>
    <?php echo get_post_meta($post->ID, 'page-heading', true); ?>
<?php else : ?>
    Normal content
<?php endif; ?>

You should be easily able to add this to the page template or to a new template according to your need.