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.
Zabbix - Track, record, alert and visualize performance and availability of IT resources
UptimeRobot - Free Website Uptime Monitoring
Statista - The Statistics Portal for Market Data, Market Research and Market Studies
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.
Montecarlito - MonteCarlito is a free Excel-add-in to do Monte-Carlo-simulations.