Though I've always said it should be a one-way / connectionless transfer of the OS data to the sensitive computer, with the human mind as the bridge to a connected machine. Thing is, we actually do this some places, but air gaps don't work. People say they do but they don't. Someone fucks up at some point.

ASIC + no interfaces might work. But sensors are essentially interfaces, though they're much harder to exploit, and if you have no sensors and no interfaces then the device isn't going to be able to do anything useful.