Cachet - Cachet is a free, open source status page for your API, service or company. Built with all of the features that you'd expect from a status page.
Website Checker Tech - WebsiteChecker.Tech is SaaS tool that detects SEO and availability issues of your website, making it easier for you to fix them.
Status.io - Status.io is a platform for system status pages and status notifications. Companies rely on Status.io to track outages, schedule planned maintenances, broadcast status notifications, and much more; and their customers love the transparency.
SEMRush - All-in-one Marketing Toolkit for digital marketing professionals.
cState - 🔥 Free & open source under MIT!
Sitechecker - All-in-one SEO platform including rank tracker, website SEO audit tool and website changes monitoring. Detailed reports by 100+ parameters with how-to-fix guides.