PagerDuty is a tool that helps manage on-call staff by setting alarms to escalate tickets through the appropriate channels. It integrates with existing monitoring systems such as Nagios, RightScale, etc., and allows users to configure their on-call schedule and business rules for escalation. Additionally, PagerDuty offers voice notifications in addition to SMS and email alerts, allowing team members to receive audible notifications that can be suppressed or resolved directly from the call. This tool is part of Twilio's platform, which provides a range of resources for developers, including API reference documentation, SDKs, helper libraries, quickstarts, tutorials, ebooks, industry reports, webinars, and a developer community hub called Ahoy.