GameKit is not an emulator. It has native support for .blend file games and uses Bullet Physics (same physics system in Blender). Graphics are rendered with Ogre.
The major difference between BGE and GameKit is that GameKit uses Lua instead of Python, so any Python scripts your game uses will need to be ported to Lua. The GameKit API is not very well documented (last I looked). You have to find it in the source code.
Also, not all logic bricks work in GameKit… again, documentation is sort of sketchy on this. Many bricks are supported, but not all.
If you know how to compile software from source code, it is not a difficult thing to make an APK of your game using GameKit. I was playing around with this back when my kids had an android tablet (which they have since broken), and it was really straightforward. Detailed instructions are here: https://code.google.com/p/gamekit/wiki/Building