Is It Down Right Now? - Network & Admin
Curler - Dead Simple Free Uptime Monitoring
Is it Down? - Is it down can check if a website is down or is it just your PC that can not access it.
Zipy - Zipy is a debugging and prioritization platform that provides user session replay, frontend and network monitoring in one.
Site Down - Site down outage and downtime reports from SiteDown.co
Simple Ops - Simplify website performance and uptime monitoring with alerting, ssl check, chrome ux metrics, multi locations