One feature of the iPad left unmentioned in the on-stage presentation but confirmed by Apple officials during the demo sessions afterward is that the iPad works not only with the $70 Apple keyboard dock but with Bluetooth keyboards as well. This could open the floodgates to other input devices.
One big question, though, is just how flexible the software will be. Even a brief encounter, it became apparent that what you can do with the keyboard is limited to entering text. If you are sitting at the keyboard, nearly all navigation still has to be done by touching the iPad screen, which is ergonomically less than ideal.
Designing a navigation device for use with an all-touch interface is tricky; I find the D-pads and trackballs included on Android devices awkward. But with a separate keyboard it could be an attractive option, if only to avoid the need to reach out and touch the screen every time you need to do anything. Do the iPad human interface device drivers include support for things such as touchpads as well as keyboards? We don’t know yet.
We also don’t know whether the keyboard support of the iPhone OS 3.2 or future versions will be ported back to the iPhone or iPad Touch. You can physically attach the iPad keyboard to either through the 30-pin connector, but the software in the device would have no idea of how to handle the input because there are no device drivers. I find the idea of using a separate keyboard with an iPhone or Touch a lot less compelling than with an iPad, but I’m all for the freedom of users to do whatever they want.