Your infra is relying on an ISP and colo and the power company and maybe even the Post Office. You're always relying on something that's not you. Personally I'd rely on pre-paid AWS. If all of us-east-1 goes down for days then we probably have bigger problems.
That's what I thought; this tool is "kicking the can" to whatever third party service you're using. So, it's essentially just a tool that will ping stuff for you in a slightly more convienent way?
Systems always rely on something. PagerDuty has been very reliable for years and we use it for alerting, so relying on it more isn’t a big ask. I plan to support multiple integrations so you could get alerted from multiple streams.