Creating a Custom International Calling Card with Twilio` is an article that describes how to create a custom international calling card using Twilio's services. The author created a simple application that allows users to call a US number and have it forward to various international destinations through a menu system. The application uses PHP and TwiML (Twilio Markup Language) to handle incoming calls and connect them to the desired international numbers. The article highlights the benefits of using pay-as-you-go calling cards, which allow users to only pay for the amount they use, rather than being stuck with a prepaid card. The author also mentions that this application can be expanded into a business opportunity, such as creating custom pay-as-you-go calling cards.