silverstripe-environmentcheck/code/DevHealthController.php

<?php

class DevHealthController extends Controller {
	/**
	 * @var array
	 */
	public static $allowed_actions = array(
		'index'
	);

	/**
	 * @return EnvironmentChecker
	 *
	 * @throws SS_HTTPResponse_Exception
	 */
	function index() {
		// health check does not require permission to run

		$checker = new EnvironmentChecker('health', 'Site health');
		$checker->init('');
		$checker->setErrorCode(404);

		return $checker;
	}
}