I'm imagining a "stealth" wifi controller on one of the custom chips, hung onto a pin connected to an internal antenna realized on an internal copper layer of the motherboard. If you used a non-standard frequency and protocol, who would know?<p>You could probably get an okay transmit-only signal with fairly unremarkable on-chip hardware (say, a simple PCM) and something that didn't look <i>too</i> much like an antenna even if you X-ray'd the board. I'm guessing that a similarly stealthy receiver would be noticeable due to required external discrete components (e.g., amplifiers, filter networks).<p>Plonking down a whole chip for "secret wifi" is likely overkill.