A developer built a Twilio Voice app that allows users to leave their New Year's Eve wishes for the world, which will be read out on a massive call at midnight. The app uses the Twilio REST API to handle incoming calls, gather recordings from callers, and initiate an outbound call with the collected recordings. The developer plans to add more functionality, such as allowing users to input a friend's phone number to share their wishes, but has not yet completed this feature due to time constraints. The project is part of a larger effort to create a social platform that connects people worldwide.