SE Ranking - All-in-One cloud-based SEO software for agencies, marketing teams and webmasters
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.
DeskAlerts - Send alerts to any corporate device: PCs, phones, tablets, etc.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
SEMRush - All-in-one Marketing Toolkit for digital marketing professionals.
Better Uptime - We call you when your website goes down