Ask HN: Biggest Alternatives to Pingdom?

Hi HN. We've used Pingdom for over a decade but in the past year the alerts have become increasingly unreliable. I never get alerts on my phone anymore despite triple checking every setting and interacting several times with their support people (who kinda just stop responding).

We added Slack webhook integration and started using a Slack channel as the alerting piece, which is OK, but Pingdom doesn't seem to honor their "Alert only after down for more than 10 minutes" setting when sending webhooks to Slack. So we get bombarded with tiny up/down up/down alerts when any minor glitch happens (even network connectivity glitches), which is why we set the "Alert only after down for more than 10 minutes" in the first place. We opened a support ticket, but given past support responses from them, we are not hopeful for a solution.

Long winded intro to the question - what would you recommend as an alternative to Pingdom? Looking for someone who's stable, established and not going anywhere obviously.

Thanks in advance.