As an alternative to HTTP/HTTPS requests, you can "ping" checks by sending email messages to special email addresses.
By default, Healthcheck will consider any email received at the displayed address as a "success" signal. You can also configure Healthcheck to look for specific keywords in the subject line or the message body to decide if the message is a "start", a "success" or a "failure" signal. You can set up the keywords in the Filtering Rules dialog:
Consider a cron job that runs weekly and sends weekly newsletters to a list of email addresses. You have already set up a check to get alerted when your cron job fails to run. But what you ultimately want to check is if your emails are getting sent and delivered.
The solution: set up another check, and add its email address to your list of recipient email addresses. Set its Period to 1 week. As long as your weekly email script runs correctly, and there are no email delivery issues, Healthcheck will regularly receive an email, and the check will stay up.
Emails are more susceptible to random delivery delays than HTTP requests. You may need to increase the grace time parameter for your checks to account for the possible email delivery delays, and avoid false alerts.
Tracking job durations (using the "start" and "success" signals) will be less accurate when pinging via email, and may not be feasible at all for jobs with very short durations.