SEMRush - All-in-one Marketing Toolkit for digital marketing professionals.
Checkify - Super minimal, simple and inexpensive 24/7 uptime monitoring
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.
Checkout X - Checkout X is an all-in-one, checkout platform optimized to maximize conversion rates and revenue on WooCommerce stores.
Moz - Backed by industry-leading data and the largest community of SEOs on the planet, Moz builds tools that make inbound marketing easy.
Curler - Dead Simple Free Uptime Monitoring