Desktop Virtualisation solutions are VMware Fusion, Parallels, or Virtualbox. In case you are unaware of the difference Boot Camp is not a virtualisation solution it is a way of running Windows operating systems directly on Mac hardware just as if it was a real PC. The same would apply for example to trying to run VMware ESXi, this also has to be installed and run directly and not inside a virtual environment.
In your case Hyper-V would be running Windows 8 itself, and the Windows Phone 8 SDK emulator. You could then run multiple Windows 8 instances via Hyper-V via Boot Camp. Hyper-V can then host its own VMs in this case the Windows Phone 8 SDK emulator. This will result in Hyper-V running directly on the Mac hardware i.e. If you want to use Hyper-V you will need to install it via Boot Camp. This is not supported and I believe most permutations of trying to run a VM inside a VM even if both are Windows would have the same problem. The issue is that you are trying to run a VM inside a VM, that is you are trying to run Hyper-V inside a VM.
