NooDS is an emulator that runs on many different platforms. This is the official Play Store version and is not a third party port. Source code and other downloads can be found here:
https://github.com/Hydr8gon/NooDS

Notable features:
- Use emulated BIOS or real files if provided
- Upscale 3D graphics using accurate software rendering
- Take advantage of multiple cores for rendering
- Configure screen layouts with a variety of settings
- Map inputs to physical buttons or controllers
- Save and load emulator states for debugging
- Active development; more will be added