Is it possible to add an item the Post Publish panel?

You can hook into 'post_submitbox_misc_actions' or 'post_submitbox_start':

add_action( 'post_submitbox_misc_actions', 'wpse_45720_submitdiv_extra' );
add_action( 'post_submitbox_start', 'wpse_45720_submitdiv_extra' );

function wpse_45720_submitdiv_extra()
{
    print '<pre>' . current_filter() . '</pre>';
}