Dynosaur is a simple Sinatra app that exposes a Heroku app via SMS, allowing users to scale their dynos up and down using text messages instead of the traditional command-line interface. The app was created by Twilio's team in response to a hypothetical scenario where a developer would be unable to access their website due to technical issues while out on the town. With Dynosaur, developers can easily spin up or down their dynos by sending a text message with specific arguments, making it a convenient and efficient way to manage their Heroku apps. The app is easy to implement, requiring only a few lines of code and minimal setup, and provides an alternative solution for managing Heroku apps in real-time.