To me, this solution is too much leaning toward graphing and that's not the primary feature you need to health check services.

Also Prometheus only saves 15 days worth of data by default and since they aren't willing to develop down sampling, it's not good to keep any long term history of the metric but you can overcome this by using InfluxDB as the storage but I would rather use something like monit which is simpler and easier to setup and gets the actual job done well.