Display a custom page template/view if a "rssa" GET parameter is placed in a post's URL

gistfile1.php

// If the query parameter is passed, use a different article template than the usual 
// (this one has no header/footer).
function rssa_content_mobile_view() {
	if ( isset( $_GET['rssa'] ) && is_singular() ) {
		require '/some-path/article/view.article.mobile-view.php';
		exit;
	}
}
add_action( 'template_redirect', 'rssa_content_mobile_view' );