Hyperping - Cheap uptime and performance monitoring with detailed reporting and flexible alerting
StatusNotify - StatusNotify monitors the status of 250+ cloud services.
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.
IsDown App - Monitor all your cloud services status pages in one place
Checkify - Super minimal, simple and inexpensive 24/7 uptime monitoring
Ctatus - CTATUS helps you monitor your external dependencies, catch problems before your clients, and get leverage over your competitors.