TroglOS is a playful, but working, example of how to create a virtual devboard from components like Qemu, Linux and BusyBox. It can also run on actual HW, currently Raspberry Pi. Use the build framework in TroglOS to test your embedded applications before the actual hardware arrives. Or as a stable reference when said hardware starts acting up -- as it invariably does ... you can even use it as a reference to other embedded Linux build systems. TroglOS is relatively clean and vanilla, the intent is to keep it as close to upstream sources as possible.