Patrick McKenzie is a Twilio enthusiast who has built several successful applications using the platform. His first Twilio app was an automated secretary that used Twilio SMS and voice calls to intercept calls and provide responses. He later built Appointment Reminder, a more complex application that sends appointment reminders via SMS and phone calls. Patrick's approach to building Twilio apps emphasizes simplicity, reliability, and scalability. He uses state machines to model the behavior of his applications and tests them thoroughly using automated tools. Patrick also discusses various best practices for building high-availability Twilio apps, including using Scout Monitoring System, God, and Redis to detect errors and prevent downtime. Additionally, he shares tips on how to build reliable Twilio apps, such as using Voice Actors instead of the `<Say>` verb, playing messages in a loop, and using Zapier to integrate with other APIs. Patrick's passion for Twilio is evident throughout the article, which showcases his expertise and enthusiasm for the platform.