Checkly uses multiple tools to monitor their platform and competitors' tools, but still heavily dogfoods their own product due to engineers liking it and finding it easy to monitor. They use Checkly for API Monitoring, Security Monitoring, and Upstream Provider Monitoring, which helps ensure the reliability and speed of APIs globally, security practices, and preemptive issue resolution with upstream providers. This approach showcases Checkly's practical applicability and resilience, reinforcing its position as a robust and adaptive monitoring tool by integrating it into critical facets of their operations.