Would like to recommend PHP Server Monitor.
PHP Server Monitor is a script that checks whether your websites and servers are up and running. It comes with a web based user interface where you can manage your services and websites, and you can manage users for each server with a mobile number and email address.
- Monitor services and websites.
- Email, SMS and Pushover.net notifications.
- View history graphs of uptime and latency.
- User authentication with 2 levels (administrator and regular user).
- Logs of connection errors, outgoing emails and text messages.
- Easy cronjob implementation to automatically check your servers.