It's a commonly used scenario to test response time and throw the alert in case of high response time. I used simple PHP code for the same.
you can use this function to get response time.
$ch = curl_init($url);
$info = curl_getinfo($ch);
// echo 'Took ' . $info['total_time'] . ' seconds to transfer a request to ' . $info['url'].$_GET['env'];
$rs_time = $info['total_time'];
$responsetime = getResponseTime("url");
This is a simple implementation and you can set up a corn and schedule this file as per your need.
In selenium: You can get an URL and on the basis of an element present in the web page can log the time. But it's not a good solution for checking response time.