Suprvise is a real-time health monitoring and errors tracking dashboard.
UPDOWNtoday - UPDOWNTODAY allows you to check whether the website is down or not.
WebGazer - Monitor your website's availability with WebGazer, review its performance and get instant notifications when your website goes down. No installation required and free plan available.
Is It Down Right Now? - Network & Admin
Monitority - Simple website monitoring service (sms/email alerts)
Site Down - Site down outage and downtime reports from SiteDown.co
Hyperping - Cheap uptime and performance monitoring with detailed reporting and flexible alerting