SIP Registration allows users to connect SIP-enabled devices or softphones directly to Twilio's Voice API, enabling advanced call-handling logic and flexible routing options. The service is free for multiple device registrations per user and offers the same Programmable Voice pricing as making and receiving calls. Twilio has already seen adoption in industries such as contact centers, with Serenova using SIP Registration to expand its contact center capabilities, and internal use within Twilio HQ, where it simplifies communication costs and expansion into new locations.