TaskyPro is a simple cross-platform todo/task application sample that allows you to track todo tasks. It illustrates proper application architecture layering and uses a common code base for the Business Layer, Data Access Layer, and Data Layer layers. It then separates out the User Interface and Application Layer into the appropriate device-applications.
The application runs on iOS and Android with a set of common classes shared across all platforms. It uses Shared Asset Projects for the common code that is referenced from all platform-specific projects.
NOTE: it also supports some basic iOS localization to Spanish and Japanese.
The equivalent app written with Xamarin.Forms is called Todo.
Bryan Costanich, Craig Dunn