The OnSite Clarity application is a sales management tool that was available in the fall of 2009, integrating Adobe Flex and PHP to manage outbound and inbound calls, voice mail, and call management using Twilio. It aims to empower sales teams with better tools for day-to-day activities, providing features such as click-to-call functionality, call routing, and voice mail management. The application also offers resources and documentation, including API reference materials, SDKs, tutorials, ebooks, industry reports, webinars, best practices, code samples, and inspiration from Twilio's developer community hub.