When the iPhone was first announced, I wrote a little post The Real Revolution in the iPhone Is the Fully Programmable User Interface. At the time the iPhone has no SDK, no App Store, nothing more than a cool looking phone with a touch interface.
The genius of Steve Jobs however has always been that he sees beyond just another new product (though sometimes it seems like it takes him a while to realize it) and into how the product will work together with all his other products. Everything Apple does now is part of a whole collection of interacting parts, all of which enhance and feed off of each other. The iPhone is after all just a little OSX Mac with a digit friendly interface. Oh and it's also a phone (unless its an iPod!).
Now that there is an SDK (and I am working with it) I can really see how the current hardware devices are only the beginning. There is a whole future ahead for the "iPhone" that we haven't even seen more than a taste of.
Of course you can argue that other people are working in the same direction (Android, etc) but I'm an iPhone developer so I'm a bit biased. But with Steve's focus on making everything work together, and only when it makes sense (at least to him), I fully expect Apple is fully aware of where this can go.
The whole point of this as a platform is that are a whole mass of needs for an interface to computing functionality that rests in your hands, and not on a desk or lap. Cell phones were about the first mobile digital devices but they lacked real usability and especially lacked real programability. Sure the manufacturer could stick in some cool apps, but the usability was always limited by the buttons and tiny screens. I always thought the early Blackberries were more thumb torture devices than great examples of computing devices. A mobile computing interface device should be as free of preconceived design limitations as possible.
A long time ago, I thought of what a mobile device could be like (and it wasn't original with me of course) that I called a WIND - Wireless Interchangeable Network Device (yes I know about the netbook from MSI called that). The idea came from the PADD in Star Trek - The Next Generation. This was an interface device that adapted itself to the user to provide portable access to information.
My musings on this was that the device was generic (i.e. it could be used for many purposes), always network connected wirelessly, and interchangeable so that you could pick up any particular device laying around and it would adapt itself to the exact view you had the last time you used any device anywhere.
In this way the WIND would appear to be yours, yet you never had to "own" one at all. Sort of like a Windows Profile (ugh) but global to the internet (or whatever network it was part of). These devices could be left anywhere in (hopefully) great quantity, free for use by anyone and able to be used as long as necessary and then discarded for someone else to pick up.
The key to making this concept work was what I called a "secret decoder ring", some kind of device or biometric access that invisibly identified you to the device as long as you worked with it. The point was making it instantly adapt to the user without any work on the user's part (such as enter a name and password). When you stopped touching it, it would become generic again (thus logging you off) but keep a local copy of the session in case you picked it up again (still with your "ring" of course).
What does this have to do with the iPhone as a platform? It looks like the start of such a WIND device, all it really lacks is the decoder ring (and a lot cheaper price!). Having a device with no mouse or keyboard and can be adapted in software for almost any purpose is a tremendous opportunity. Even if the WIND idea never happens, future hardware devices in the iPhone platform may be completely unconnected to being a iPod or iPhone or iMac but could be (in a paradoxical way) customized for particular uses, such as hospital information or delivery capture or inventory management; yet remain completely generic on the inside and in the interface itself. After all, many hand operated tasks do not require typing and mice, which are after all only two ways of entering information, not the only ways. If I am doing inventory, I can get a lot done with bar code scanning and entering values. A device that does this easily and yet can be customized on the fly for the product or the location or even the time of day is far more useful than a device that requires one to learn specific key punches or codes to enter stuff.
So will Apple build these types of devices, more generic or more custom, all based on the Touch interface? I certainly hope so, but only when Steve thinks the time is ripe (or the market starts bugging him!).
After all, phones are no big deal by themselves, but finger operated fully programmable UI devices are. WIND or no wind, the future of digital devices is, well, digits!