As you can see from the picture, this project is mostly complete. I will be adding more details soon, but here is a quick overview: I've used a Teensy 3.1 to run the emulation and a 2.2 inch SPI screen for the display. Power comes from wither on onboard LiPo battery or via USB. Dimensions are 79mm by 48mm by 20mm.
Source code and design files for the 3D printed parts cane be downloaded from this page.