My initial reaction to the teasers for 3.0 was excitement. My understanding of the opening up of the accessory port to developers would allow for fun innovation. I was wrong.
The dream I had was to be able to connect my iPhone, via USB, to my camera(s). This would allow my phone to act as a remote control, and as an external screen for photos & video. The gPhoto libraries looked like they could provide a starting point.
What is actually provided doesn’t allow for straight USB connectivity.
The External Accessory support requires a validated accessory, with appropriate hardware protocols, to work. You also need to be a member of two programs, iPhone Developer and the Made for iPod program.
I can’t see Canon or Nikon releasing cameras with iPod dock connectors or protocols.
This doesn’t leave many options. One is to build a hardware device that is USB in one end and a custom protocol out the other. This gets tricky fast as the hardware device needs to figure out the camera support. And I really liked the idea of a simple cable connection being all that is required.
The second option still has some merit: WiFi. There are a few downsides. Firstly, you need a camera that supports WiFi or an expensive adaptor. This limits the audience for the app. Secondly, you need a wireless network available and to also manage pairing between your iPhone and your camera. This starts to be more equipment than desirable.