To encourage Y-Combinator companies to try their Twilio API, the company is offering a gift certificate to cover the first $133.70 in Twilio use. This allows developers to leverage existing web development skills and resources with an in-cloud API for voice communications. The gift certificate can be used to build professional voice apps, such as answering calls to a company's 800 number, which can provide a more convenient way of communicating than traditional cell phones. By using Twilio, Y-Combinator companies can improve their communication and digital engagement experiences with the help of customer engagement experts through various resources available on the Twilio website.