These all now are virtual state machines, which store some state and convert all kernel/bus behavior to interaction with connected via network devices.
At the moment there are lot of such devices - exists for sure many full featured, like Raspberry; but also there are network connected ATA drives, network connected sensors, RAM, ROM (Flash); BTW IEEE 1394 FireWire is serial interface, could been used as networking bus; exists adapters ethernet-usb (and many commodity devices work well with such connection), so virtually anywhere could been considered as connected via network bus.
Even exists USB 3.0 to PCIe adapter, to use PCIe device throw USB connection.
And in reality exists problem, that FireWire so distributed, that it where possible on Macs with FireWire interface, to read memory via this interface.
So hardware and software exists, but need some steps to make it's usage safe.
