unityGB allows you to run a Game Boy ROM in your Unity project. Globally, it's a Game Boy emulator written for Unity and it's totally free and open-source.
It has been written in C# and is only using Mono allowing you to export the project to any platform supported by Unity. Also, unityGB has been released as Open Source software under the GNU General Public Licence. This means that you can download the source code, find out how it works,...
unityGB - Emulator Game Boy for Unity [RELEASED]