I guess I understand what William wants, practically not an "emulator" but a simulator for each of the components of a phone. So that the various interactions between components can be studied. So a processor simulator, a chipset simulator & motherboard controllers, a memory simulator, and if possible for various sensors. That is, not just an emulator of the entire operating system, but separate software components that can be studied in several simulators.
I have no idea if there are such programs for simulation, I guess every phone manufacturer has this, just that they are used for strictly internal purposes, not being commercial.
It is possible that such simulation software may exist in technical universities, within computer labs or possibly passionate programmers to develop such simulators.
I would say that this field is very small among the passionate, being required high level knowledge, so it is possible and such programs to be difficult to find and even use.
That's my guess about what William wants.