GoReplay - GoReplay is an open-source tool for capturing and replaying live HTTP traffic into a test environment.
Pingdom - With website monitoring from Pingdom you will be the first to know when your website is down. No installation required. 30-day free trial.
Testlio - Testlio is a community of expert testers that help companies release their apps with highest confidence
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Assertible - Assertible software provides you with a simple and quick way to monitor your web services. It comes with automated QA tools that users can utilize to test and monitor their web services on different platforms and environments.
Better Uptime - We call you when your website goes down