As a life-long gamer and, more recently, a tablet game developer, I spend a fair amount of time thinking about what does and doesn't work with tablet UI design, which naturally leads to some musings on how I'd build a tablet from the ground up if I had the chance to. I know some people are already thinking about contact lenses and virtual touchscreens that get projected onto thin air, but I'd predict that we're going to have tablets for a good long while, I think they'll outlast traditional mouse/keyboard/monitor setups by at least a couple decades... so let's set about unlocking their untapped potential!
1. Tactile Feedback
One of the great things about a tablet is how intuitive it can be if done right. Look at a game like Flight Control, just draw a flight path on the screen and airplanes will follow it... don't need much more explanation than that. The fact that they make iPad games for cats, dogs, and babies speaks volumes to how a well-designed tablet interface plays to instinctive behavior rather than learned behavior.
But sadly, where our instincts want multiple senses to agree with each other, whatever you touch on a tablet is just going to feel like glass no matter what it looks or sounds like. This isn't a terribly big problem when you're writing an e-mail, but in a fast-paced game you're going to want to keep your eyes on the action and not on helping your fingers find the buttons. This isn't a problem for traditional controller-based games since they're designed with tactile feedback in mind. And while it's possible to design a game without buttons in it, it can be limiting. Sometimes, you just need to throw a button on the screen, especially if you're porting a console game to a tablet, and it would be great if those buttons felt as natural as they do when you've got a controller in your hand.
I've seen a few different approaches to this, all of which seem to be from three or four years ago in articles or videos that end with the hopeful but now inaccurate phrase "and we expect these to be commercially available by 2012." There's the display that physically raises bits of the display (because how better to make a button feel three-dimensional than to actually create the shape of one in three dimensions?), but what really intrigues me are the displays that take advantage of the way our skin senses touch and create electrical fields that can mimic other textures. I haven't experienced either of these so I couldn't tell you which approach I favor (although I can't argue with "let's just have both").
On top of that, let's throw in old-school rumble technology. How better to please your lizard brain than by actually making the screen rumble during a giant explosion? But rather than just throw a single shaking motor on there like the good ol' N64 Rumble Pak, why not take a look at what Valve's doing with their Steam controller? Articles seem sparse on the specifics but all I keep hearing is that the force feedback is crazy well-done.
2. Stereo freaking sound already.
I don't know what Android tablets are like, but my iPad has just a single speaker on it that tends to get covered up by the hand you're holding it with. What I'd really like to see is four speakers, one on each side of the device, and use the same software that orients the screen to appropriately assign the speakers as left, right, and center channels depending on how you're holding the device. You don't need big honking speakers to get a good sound experience these days, just check out the 3DS. Two speakers each smaller than a dime and you get a pretty good 3D sound experience out of them. Come on, tablets, it's time to up your game.
3. Better color gamut coverage
The latest displays have taken resolution about as far as we're gonna take it. Where to now? Well... standard RGB displays sadly leave out huge chunks of colors that the human eye can percieve — I find this most noticeable in the range between blue and green, but there's shortcomings all around the color wheel. Every once in a while you see a company throw a yellow or cyan primary into their monitor to try and cover these gaps but thus far it hasn't seem to have caught on (in part, I'd wager, because you'd need special software to really take advantage of 4+-channel color)... but I'd personally love a device that shows me more of the colors I can see.
4. Pressure-sensitive touch
I've had a Cintiq for several years and a Wacom tablet before that, and I've loved them both. One of the key differences you get from either of those devices compared to an iPad touch screen is the idea of pressure-sensitivity. You can bear down with your stylus to make a thick line, or gently glide it across the screen for a thin one. Or, you know, you can configure your brushes to do other fancy stuff, too, that's just one example. My iPad can't tell gentle from firm, it just knows "touching" and "not touching," it would be great, especially for drawing apps -- but also for games with on-screen-buttons -- to be able to register changes in pressure.
And while we're talking about it, it would be nice to have some better-precision styluses than those eraser-sized foam-tipped ones.
5. Any-Angle 3D
I can hear some of you groaning already, denoucing 3D anything as a gimmick that just needs to die already. I may be in the minority, but I own a 3DS and I actually like its most-mocked feature. But it could stand some improvement. It's a little tiring to need to hold the 3DS a certain specific angle to your face and a certain distance away. Playing a game like A Link Between Worlds sometimes you get lost in the 3D illusion and then you try and crane your head to one angle to see something better, and then the illusion is instantly broken.
So, what I'm thinking... why not have the camera track your gaze and adjust its 3D accordingly? I'll admit, I don't know much about how lenticular displays work, I'm not sure how possible it would be to make a 3D display that works just as well in portrait orientation as it does in landscape... a quick Google search seems to indicate that this would indeed be possible but it seems like there's issues with it to be worked out still.
6. Touch-sensitivity on the back, not just on the front.
One of the most common criticisms I've heard about the control scheme in our current work in progress, The Day We Fought Space, is that while it's very intuitive, your hands block some of the view of the action when you're steering the ship and aiming your weapons. We have some alternate control schemes available that mitigate this issue, but since the only way to interact with the screen is by touching it, it's never going to go away completely.
Unless... you could have touch input somewhere that isn't the screen at all, like the back of the device? The PS Vita has a setup like that, if I'm not mistaken. Admittedly, you'd lose some of the intuitiveness of touching the things on screen you want to interact with, but throw in the tactile feedback I mentioned in point #1 and you could have a seriously powerful gaming interface in your hands.
Unfortunately, what I expect will be the biggest hurdles in getting a tablet like this on the market will not be technical ones but legal ones. I'm sure most of these ideas, even the ones I might think are original ideas, are already patented by some company jealously guarding their secrets, and getting the best of all worlds fused into a single device will remain a legal impossibility. But that's a rant for another day...