UptimeRobot App - Web, SSL, ports & Cron-jobs monitoring
Hyperping - Cheap uptime and performance monitoring with detailed reporting and flexible alerting
Robodash - Cron and uptime monitoring dashboard
Pulsetic - Pulsetic makes monitoring your SaaS products simple and easy with Status badges to show the status of the site without changing pages and you will also be alerted when your site goes down.
DomainWatch - Domain Monitoring Made Easy
UptimeRobot - Free Website Uptime Monitoring