Binary Canary

Website monitoring service that offers a comprehensive free plan with: * escalation levels (if a first-responder contact doesn't acknowledge the downtime, another...

Commercial

Observu

Website and server monitoring with alerting via e-mail, SMS and phone calls. Has a dashboard to easily monitor 100 or more services at a time by sorting them depending...

Commercial

AppSignal

Monitoring for Ruby developers. All the metrics and alerts you need to keep your app running smooth. Support for Rails, Rack, Sinatra, Padrino & Grape.

Commercial Mac OS X Windows Linux BSD

ServersUp.net

ServersUp.net can check a number of different services on different hosts to make sure those services are up and running. It will send alerts when the statuses change.

Free Web

Servitor.io

Servitor is the easiest way to monitor your servers and website for resources, uptime, ssl certificates, mixed contents en broken links.

Freemium Linux Web