Heartbeat is a simple way to check a process's vital signs. Use it instead of Monit, Pingdom, Uptime Robot, or any combination thereof.
There's no setup. Just open up a terminal and type:
This will create a new heartbeat that will alert "firstname.lastname@example.org" in 60 seconds. You can postpone this alert by running the same command again, or you can stop it altogether by sending a cancellation:
The most straightforward use case is for keeping tabs on sensor data, but I can imagine using it wherever downtime requires your attention. I use it to monitor several Raspberry Pis (which I use for all sorts of things around the house).
Check out the README for the full documentation and more usage examples.