"Convergence" is something of a buzz-word these days, as portable devices include ever-more features. Some of this is due to the simple fact that as computer manufacturing technology becomes more advanced, more electronic circuits can be squeezed into a given device. Some of the convergence phenomenon
is due to the simple desire for people to carry less numbers of different things around with them. Already sales of ordinary wristwatches is diminishing, due to the fact that cell phones have clocks built into them. And some of the convergence phenomenon is due to the fact that a computer processor is a general-purpose device; it can process business data, game data, voice data, music data, video data, etc. All data is just numbers, anyway, to a computer, so every possible kind of data is conceivable to be processable, by some future Ultimate Convergence device.
In this Idea I will call that device "the Converged", implying that all those different things are built into it. Camera, microphone, phone, calculator, clock, music player, video player, computer, etc: What will it look like, and how convenient will it be to use?
Well, first you need a place to carry it that leaves your hands free, if you want it to be convenient. That almost certainly means a holster of some sort. While I'm sure that a lot of cell phones and other stuff have holsters already, I don't know how many of them are just afterthoughts -- "The phone looks like this, so make something to hold it."
I'm suggesting a synergy in design, where the Converged and its holster effectively work together so that the device can be as easily pulled from its holster, and as easy to put back, eyes closed, as a gun. It must be as easy to hold as a gun; the handle must be a natural "fit" for the hand. It must be as safe to handle as a gun can be, without the holster pushing the wrong button. But it cannot look like a gun; where would you put the display screen if it did? Unroll it from the barrel like a "Bang!" message? Maybe...but no, that would be too flimsy, especially while you still need a way to input data.
I tend to think that an old fashioned clothes-iron has a more appropriate shape for the Converged. (We only want the SHAPE, or something approaching it, and not the weight of an iron, of course.) An iron's shape features a flat side, suitable as a display screen, and it has a true handle, which can be ergonomically constructed, attached to the other side. Often this handle is attached to the main body of an iron in two places, but because the Converged will weigh less, and because we want to be able to holster it, this handle should only attach to the main body at one place.
An iron has a pointy end, which we might not wish to copy for the Converged. A square or rectangular shape gives us a better display screen, after all. On the other hand, a pointy end makes for an easier insertion into a holster, and we still need a place outside the screen to put various control and/or input buttons. Here I will assume that something of a pointy end (a curved end?) is retained, just so I can use it as a reference point (believe it or not, no pun intended!) in the descriptions below.
Let's imagine the Converged being holstered, and you want to access it. The handle is outside of the holster, of course, so you reach down and grab it. A natural grab means that the handle must be positioned at an angle from the vertical. You withdraw the Converged, and raise it to view.
You see that as you have raised it, you have also turned it around, so that while the pointy end was downward in the holster, now it is upward. The connection point between the handle and the Converged is beneath your grip on the handle. You can easily hold it so that the face of the screen is toward you.
Once removed from the holster, you can now manipulate the Converged. First, because even though the iron-shape allows a much larger screen than just about any handheld device currently on the market, if we want this to also be a full-fledged portable computer, the screen needs to be even bigger. No problem, just unfold "leaves". Now the screen is at least twice, and perhaps several times, as big as before. Fancy folding gadgetry, that leaves us with no hinges in the middle of the display surface, is just an engineering problem, and probably already solved.
Note that the total volume of hardware doesn't change just because we have unfolded it to a different shape. The electronics for the Converged is assumed to fit, even if the inside of the handle also has to be used.
Note also that the more surface area that can be exposed by unfolding, the better. There is at least one flat-panel display technology out there (see link) which could in theory have a "backing" of solar cells, to power the Converged. The display technology does not emit light; it uses "interference" phenomena to selectively reflect ambient light, and so is very low power (and all light not reflected is theoretically absorbable for power).
Several varieties of data input are possible. There are the buttons previously mentioned. There is the back side of the Converged, where the hand holding it may be able to use a finger or two to press some other buttons. There is video input and you have one hand free, so one-handed sign-language-recognition is a possible data input method. If you have a place to set the Converged down, so you can do two-handed sign language, then the device naturally stays upright, since the bottom of the handle, behind the screen, now works as a support point.
There is audio input, so imagine a wireless connection to an insulated "subvocalization collar" that you wear. This could provide for a voice-recognition data input method that is not much affected by ambient noise. (And the collar should be solar powered, too!) Also, while not a data input method, it would make sense for the collar to feature "ear buds" so that the wireless audio communication is two-way, and doesn't disturb the people around you.
There is touch-screen technology as another data input method. This means the Converged has a three-layer "screen", the bottom layer being for solar power, the middle layer being for display purposes, and the upper layer being for data input. Well, what else do you expect of something called the Converged?
That about wraps up this description of the hardware. Almost all else is just software, hopefully with all the bugs worked out, and wireless data transmission to the phone company, the Internet, your business computers, or other places.