Azure Load Balancer - Azure Load Balancer delivers high availability and network performance to the applications.
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.
nginx - A high performance free open source web server powering busiest sites on the Internet.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
AWS Elastic Load Balancing - Amazon ELB automatically distributes incoming application traffic across multiple Amazon EC2 instances in the cloud.
Better Uptime - We call you when your website goes down