public function getPerformanceSummary($checkId, $resolution = 'hour')
	{
		$client = new \Guzzle\Service\Client('https://api.pingdom.com/api/2.0');

		/** @var $request \Guzzle\Http\Message\Request */
		$request = $client->get('summary.performance/' . $checkId, array('App-Key' => $this->token));
		$request->setAuth($this->username, $this->password);
		$request->getQuery()->set('resolution', $resolution);
		$request->getQuery()->set('includeuptime', 'true');

		$response = $request->send();
		$response = json_decode($response->getBody(), true);

		return $response['summary'][$resolution . 's'];
	}