I haven't been able to find any documentation on hardware access via the iPhone SDK so far. I'd like to be able to send signals via the dock connector to an external hardware device but haven't seen any evidence that this is accessible via the SDK (not interested in possibilities on jailbroken iPhones).
Anyone have any pointers to docs for this or some idea of what deep dark corner i should look?
This falls into the range of capabilities that requires working with Apple to get a special license. At, I presume, a special price.
This has changed to some extent with the 3.0 version of the iPhone firmware. If PyjamaSam is correct there is still some special activity required to get the connector specifications.
It will with the new SDK (3.0):
Using iPhone SDK 3.0 your application can communicate with accessories attached to iPhone or iPod touch through either the 30-pin dock connector or wirelessly using Bluetooth.
To get the Hardware specs for the Doc connector you need to be part of the made for ipod/iphone program. But if you just want to talk to an already existing piece of hardware that supports it, the 3.0 SDK will let you access it.
I have tried applying to the made for ipod/iphone program as a individual/hobbiest, but have so far not heard anything past the "fill out the company information" stage.
chris.