Cronitor - Monitor cron jobs, micro-services, daemons and almost anything else, no setup required. Easier cron troubleshooting and no more silent failures.
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.
Dead Man's Snitch - Monitor Cron Jobs and Windows Scheduled Tasks with ease.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Robodash - Cron and uptime monitoring dashboard
Better Uptime - We call you when your website goes down