While a MarkIII player is still a distant glimmer in EMPEG's eyes, I think a good solution would be to build a PCMCIA or similar expansion slot into the MarkIII. This would allow you to buy an off-the-shelf wireless Ethernet card, stuff it into your EMPEG, and it would work both inside your car, inside your house, at your office, etc., and it wouldn't require adding any new pins to the docking connector.

Furthermore, when 3G cel phone networks are deployed, many more consumers would likely want to hook their EMPEG to the cellular network, such that they can "phone home" from anywhere. It would be most sensible for the MarkIII to be agnostic toward these various network standards and an expansion slot is probably the best way to do it.