Until today, I just discovered one can add a new monitor type called Push.

This provides you a Push URL like this (Optional parameters: status, msg, ping):
https://uptimekuma.1heal.org/api/push/U20C3xxxx?status=up&msg=OK&ping=

So a script output, like cronjobs can be monitored like this:

#!/bin/bash
# Filename: index.sh
PUSH_URL="https://example.com/api/push/key?status=up&msg=OK&ping="
INTERVAL=3600

while true; do
    curl -s -o /dev/null $PUSH_URL
    echo "Pushed!"
    sleep $INTERVAL
done

Even apps and containers starting up..

And preventative disk usage checking and other stats which @staff could integrate with Cloudron to send Push messages via Uptime Kuma.

Since I already use it for monitoring websites, I get to piggyback on the free notifications too!