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.
ServerSuit - ServerSuit is a browser based program that enables remote Linux administration, monitoring, website hosting, and server setup automation.
UptimeRobot - Free Website Uptime Monitoring
RedGate SQL Monitor - SQL Monitor helps you and your team find issues – before they become problems
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Netumo - Ensure healthy website performance, uptime, and free from vulnerabilities. Automatic checks for SSL Certificates, domains and monitor issues with your websites all from one console and get instant notifications on any issues.