What ever happened to the forearm-mounted computer?
Now, I'm not as big a sci-fi buff as many, so I can't say that it's a staple, but the idea of a computer scarcely more cumbersome than an armored bracer isn't something that yet needs introduction to the genre. There are many sizes and flavors with many kinds of I/O, but the tech behind it, for it to be practical, has always been kind of brushed over.
I'm holding my iPod touch in my hand. Including processor, battery, and hard disk, it's hardly half an inch thick. Assuming that half of that was the touchscreen display would be generous--so, if you had two matching clamshells (probably slightly curved), one or both a touchscreen, and with the rest of the hardware on the other half of the arm, it would be barely if at all thicker than one iTouch. Scale up the dimensions of the screen just a smidge and you have something almost large enough for an actual keyboard, plus a second screen for data--or, like the iTouch and iPhone, turn it on its head, or any-which-way, in order to get the computing experience you desire. (You'd have to make the processor and battery marginally better to accomodate its needs, but the iTouch runs off a 500MHz processor--it's not like we don't have the means to make better)
I'm sure the position would be awkward--having a weight on a round-ish surface like your forearm is something that would cause torque to be a big issue, as I (as others) notice with our watches every day (although, for a well-fitting watch, it isn't a problem--and I'm sure that a properly-fitted watch band up front, and a support strap in back, might deal with the torque well enough). Also, the forearm display probably isn't ideal for either typing or watching--but you'd get used to it, and even if you didn't, it's mobile computing--there aren't many solutions that get it right throughout ALL of digital history.
Still, the geek in me feels that the body-mounted computer industry has been severely lacking for far too long. And let's face it--if you can mount a display like that on your forearm, you can make it JUST the display--and carry a laptop in a backpack with a flexible cable running down your arm. There aren't many, or any, really, solutions that would let you do computing like that, while standing or walking, especially in a way that doesn't threaten imminent and trivially-executed device theft. I wouldn't walk down many dark alleys with it, but short of being ordered to take it off at knifepoint, it remains personally attached.