Cronotary is described as 'Painless periodical tasks monitoring. Cronotary makes sure your background jobs are up and running. Get instant alerts when any of your jobs fail or run longer than expected'. There are eight alternatives to Cronotary, not only websites but also apps for a variety of platforms, including Android, Linux, Mac and Windows. The best alternative is Healthchecks.io, which is both free and Open Source. Other great sites and apps similar to Cronotary are PushMon (Freemium), WebGazer (Freemium), Cronly (Freemium) and Cronitor (Paid).
WebGazer is a website and cron monitoring service. We check if your website and REST APIs are up, and notify you if anything goes wrong. You could also send periodic HTTP requests at the end of cron jobs or scheduled tasks to monitor.
Monitor cron jobs, micro services and almost anything else. Realtime alerts when your tasks and services don't run on schedule, run too long or fail unexpectedly. Easier cron troubleshooting and no more silent failures.