This is a guest post by Derrek Wayne on how he used Twilio’s API to create CustomSongSender.com, a web application that allows users to send customized birthday and Valentine's songs to friends and family. The app uses PHP and MySQL, with the front end handling user input, the back end running cronjobs to follow up with users and deliver the song, and Twilio integration for making phone calls and sending SMS messages. Derrek borrowed design elements from AwesomenessReminders.com and used session variables in PHP to allow users to re-record their customizations. The app features eight original songs written and recorded by Derrek himself, and demonstrates how easy it is to use Twilio's API to build a feature-rich application.