The External Accessory framework added in iPhone OS 3.0 does give you the ability to communicate with outside devices connected either through the dock connector or Bluetooth, but those devices must be part of the Made for iPod program. That means that they must have special hardware in them, obtained from Apple, that allows you to communicate via the protocol Apple uses. If they do, it becomes very easy to interact with them through the External Accessory framework.

Apple has made a push to open up the Made for iPod program to much smaller companies than had traditionally been able to develop iPod accessories, but there are still some hurdles to overcome when designing such hardware. An approval process with Apple is involved, along with the hardware design you ll have to do. This means that it s still not suited for one-off projects like your robotic controller, unless you plan to sell your robotic controller in moderate volumes.

However, I have heard of a few companies who are working on generic digital-to-analog boards and the like, which might be able to act as a hardware interface for your robot. Pasco attempted to show off one such board during the WWDC 2009 keynote.

I can t comment on the licensing, but you can get the connector easily: http://www.sparkfun.com/commerce/product_info.php?products_id=9601

Not for the app store, but for personal use, sure. Just link with the private IOKit framework and read http://iphonedevwiki.net for how it all works.

Note that you may need to jailbreak at some point and it will never make the App Store.

The connector is an Apple exclusive part, and Molex will only sell it to licensees that Apple approves.

If you want to use the dock connector or the BT interface, contact Apple developer relations, and join the iPhone hardware developer program. They ll ask you to sign a separate NDA from the one you ve already done as an Apple developer program member.

It s not that it s only for big corporations, it s more like the only interest they ve seen so far is from outfits like Bose, JBL, or car companies looking to implement tighter integration with the iPhone. Tell them what you want to do.

The best way is by interface iPad/iPhone to the controller (fanless PC, microcontroller with TCP/IP stack) of the robot via WiFi, and your controller programmed to communicate with the robot by any wireless protocol/physical link eg.. zigbee..