NIXStats - SaaS monitoring tool for window/linux servers and websites. Think up-time robot but with more features.
Tenable.io - Tenable.io Cyber Exposure platform helps to protect any asset on any computing platform and eliminate blind spots.
OpsDash - All-in-one solution for monitoring servers, services, uptime and databases. Curated Dashboards. Rule-based alerting.
BreachLock - BreachLock is a versatile platform that provides scalable and smooth penetration testing services for vulnerabilities.
Monitornator - Server monitoring made simple
Qualys - Qualys helps your business automate the full spectrum of auditing, compliance and protection of your IT systems and web applications.