For anyone who isn't familiar with Unicorn, it doesn't emulate any specific whole-system, it's a library/framework for emulation of just the CPU. You are responsible for hooking up the whole "rest of the world" to the emulated CPU, for whatever you might need. This includes things like emulating peripherals, syscalls, binary loading, etc.

You usually use it to build your own emulator or other analysis tool, often for reverse engineering.