Flutter is a new and free open-source framework created by Google which allows mobile application developers to create and deploy applications on both iOS and Android using one programming language, Dart, as well as one single codebase. Released in late 2017, the toolkit provides cross-platform solutions for mobile and desktop application development which is a benefit not seen in other application development tools, such as React Native. This project explores the advantages and disadvantages of using Flutter to create an interval timer mobile application which can be deployed on both major mobile operating systems. It will explore areas such as the simplicity of creating the user interface, performance of the application, the overall application development process, and integrations with external devices such as the Apple Watch and Android Wear.