That brings up an off-topic point I've always wondered about. If apple will not make it possible for third party devices to interface with the iPhone through the normal port, why do approve apps that rely on hardware using the audio jack this way?
But they _do_ allow that. You have to pay a license fee to Apple for the connectors, programming interface etc, but even without that you can do communication using one of the established protocols like MIDI. Also, you could use Bluetooth 4.0 without any licensing at all.
So the question to why they allow it is that they're not consistently evil :)
I've seen credit card readers that act as a hull for an ipod touch and connect to the data port. (Necessary in austria because the audio trick wont work with chips)