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.
D3.js - D3.js is a JavaScript library for manipulating documents based on data. D3 helps you bring data to life using HTML, SVG, and CSS.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Chart.js - Easy, object oriented client side graphs for designers and developers.
UptimeRobot - Free Website Uptime Monitoring
Google Charts - Interactive charts for browsers and mobile devices.