adelessert

WordPress’s built in cron system is clever, but notoriously unreliable. <a href="https://deadmanssnitch.com" rel="nofollow ugc">Dead Man’s Snitch</a> is a great service for monitoring any sort of scheduled task, and is a simple way to make sure that your WordPress cron jobs are working properly. If WP-Cron isn’t working properly, WordPress might not be updating itself regularly, scheduled posts may turn up late or not at all, and other features you count on might not work.
This plugin simply allows you to store your Snitch URL in the WordPress admin, and requests it once per hour. If Dead Man’s Snitch doesn’t hear from WordPress when it expects to, it’ll send you an email notification.

WP Dead Man’s Snitch

WordPress's built in cron system is clever, but notoriously unreliable.

anmari

Overview of all cron jobs, showing whether the corresponding action is present. This is handy if you are struggling to write a plugin with a cron job. If there is no action created by the cron job plugin, nothing will happen – just delete the job. 
Includes ability to delete comprehensively and reschedule the jobs. 
Shows time in wordpress timezone, not utc time, so it is much easier to understand!

amr cron manager

An excellent plugin if you want to have a quick look at the WordPress cron queue. Easy reschedule, delete and even a mass delete of all active crons.

Excellent plugin

Overview of wp cron jobs in the site's timezone. The lists show if the action exists and any arguments to the cron job.

WP Dead Man’s Snitch vs amr cron manager