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Does the iPhone SDK allow for serial port connections? Can I use RX and TX serial lines over the dock connector? I do not want to distribute the application over the app store, I want this to be a tightly controlled distribution.

So bottom line:
Can I use the dock for serial connections with the official SDK?
Can I create a program and choose to distribute it on my own? (This may even be small enough quantities that I can literally connect each iPhone to my computer)