[This was getting a bit lengthier than I intended. So I'll begin with the first two for now.]
There are lots of gadgets out there that people use to communicate with their computers. However, only two--the keyboard and the mouse--are really in broad, mainstream use. If you add controllers for games, there are a few more input devices depending on the genre: game pads, joysticks, and steering wheels. However, although game pads of one sort or another are the predominant way to communicate with gaming consoles, their use on PCs is far more limited and specific to a limited set of uses.
So is it the keyboard and mouse forever? I would be surprised, shocked really, if we were to see anything replace the keyboard and mouse (BTW, I lump trackballs in with mice because they're different ergonomic takes on the same basic function) on the desktop anytime soon. But could one or more of the devices that we see at the fringes today become something truly mainstream--if not universal, then at least a common site on your typical desktop. I think the following are potential candidates.
1. 6 Degrees-of-Freedom (DOF) controllers. Like most of the things on this list 6-DOF controllers aren't new. They've been used in 3-dimensional computer-aided-design (CAD) applications for a while and they've had price tags to match the pricey software that they've been used with. How they feel to use is a bit hard to describe but it's essentially a sort of knob that you can push down, pull up, rotate, and push or tilt in any direction. Essentially this lets you move and adjust your view through 3-D space using single control. 6-DOF controllers are interesting today for two reasons. First, we're starting to see inexpensive examples. The 3Dconnexion SpaceNavigator PE (Personal Edition) 3D Navigation Device USB ( 3DX-700029 ) is about $55 for a little device with a great feel. Second, we're starting to see 3D environments--other than space battles--where such a device could be really handy. Virtual worlds are one future possibility--especially if they get to be as important as some think they will be. But, even today, navigating through Google Earth with a SpaceNavigator is truly eye-opening. It transforms it into a whole new experience.
2. Write-able screens (most likely multi-touch). I have a basic Wacom Graphire tablet. It's just the latest in a string of tablets that I've owned over the years, but it mostly sits gathering dust. I bought it mostly to edit photos in Photoshop, but I just don't find it all the useful. The problem is that there's essentially a physical disconnect between writing on the tablet and what's happening on the screen. The two things aren't happening in the same place. Tablets are fine for tracing but I don't find them much use to create or edit something that's being displayed on the screen. I imagine that one can develop a better feel, but FWIW I've heard the same thing from professional artists. The best solution is to write on the screen. We've seen some impressive multi-touch demos of late (to say nothing of the iPhone). However, even just having affordable modest-size LCDs we could write on would be a god start. Wacom makes the very snazzy Cintiq, but at $2500, it's clearly a tool for graphics professionals. Why does this matter? I'm happy to make the argument that this is a key missing ingredient to having distributed meetings and discussions. Where's the whiteboard in such a meeting? (Please don't tell me to either do a napkin sketch using a mouse or to draw something, scan it in, and then send it to people. Ick.) A low-end and more-affordable version of the Cintiq would be invaluable for people who need to sketch out a quick idea or a concept. Add in the fact that more and more people have multiple monitors and having one of them be a writable version is a natural.
[More to follow...]