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.
Deepinfo - Know your attack surface. Empower your security.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
SecurityScorecard - Security solution to predict and remediate potential security risks across organizations and their partners.
Better Uptime - We call you when your website goes down
UpGuard - Visibility into the state of your IT infrastructure, enabling you to understand your risk potential, prevent breaches, and speed up software delivery.