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.

RapidSpike - RapidSpike is a reliability, performance and security monitoring service for transactional websites. Using next-generation synthetic monitoring & deeper than ever before data, RapidSpike is for businesses serious about protecting their online revenue

MenuBar Statistics - MenuBar Statistics is a lightweight app that sits quietly in your menu bar of macOS and displays computer information such as CPU, Disk, and Network, which is updated every 5 seconds.

Nodeping - NodePing Server Monitoring and Web Site Monitoring. Simple but powerful Internet service monitoring.

RPi-Monitor - RPi-Monitor is a tool that provides all the connected system peripherals properties and current metrics.

Webcron - Webcron - Website and Server Performance Monitoring and Online Web Cron. Reliable Cron Jobs Service with WebCron interface. The easiest way to set cron jobs.