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.
logit.io - Logit.io provides complete observability of logs, metrics and traces. The platform also offers alerting & monitoring, as well as Prometheus, OpenSearch & Grafana. Ingest any type of data to see real-time insights about your applications and services
UptimeRobot - Free Website Uptime Monitoring
Datadog - See metrics from all of your apps, tools & services in one place with Datadog's cloud monitoring as a service solution. Try it for free.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Plumbr - Plumbr is an application performance platform that provides insights to users on the performance of their applications.