Would need some prettifying, but basic code is following:
add_filter('manage_pages_columns', 'add_revised_column');
add_action('manage_pages_custom_column', 'echo_revised_column', 10, 2);
function add_revised_column($columns) {
$columns['revised'] = 'Revised';
return $columns;
}
function echo_revised_column($column, $id) {
if ('revised' == $column)
echo get_post_field('post_modified', $id);
}