DNS Max - DNS Max provides a web based DNS management software.
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.
ClouDNS - ClouDNS is a platform that allows users to keep their websites, data, and network security all the time.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
ChangeIP - The Fastest and Most Reliable Dynamic DNS
Better Uptime - We call you when your website goes down