Wearables seem designed to meet three not necessarily compatible needs:

• ubiquitous computing; constant access to your data and the Net.
• rugged computing; devices that can withstand extremes of temperature, moisture, or other environmental variances.
• hands free computing; devices that can be used in work situations where hands must be occupied with other tasks, but a data display needs to be immediately present.

The latter case is where there is a clear business opportunity; the first case has the largest "coolness" factor. Medical professionals are often in need of a hands free device, or at least one requiring a minimum of hand-keyed input. There are also industrial settings where hands free computing seems like it will have big appeal (picture the construction worker who has a popup display of relevant blueprints with him at all times on a construction project). So there are real companies putting real R&D money into making this kind of computing a viable venture.

But most of the groundbreaking work has been done by CS geeks who just want to be plugged in all the time. I confess to falling into this category myself. What fascinates and puzzles me is that none of them have used a laptop as their starting platform. Consider:

• The typical laptop supports an external monitor.
• The typical laptop supports an external keyboard and mouse.
• The typical laptop comes with a battery.
• A laptop packs all of its main systems and peripherals into a much more compact space than you could achieve building equivalent functionality with off the shelf PC hardware.

Now, the expectation is that a laptop's external monitor will be a desktop monitor, the external keyboard will be a desktop keyboard, etc. But nothing prevents you from going the other direction, and using one of the head mounted display devices on the market, or using the Twiddler as your keyboard. And nothing prevents you from splicing a laptop's power cord into one of the industrial strength 8 hour battery packs favored in the wearable community. Take these steps, park the laptop in a suitably sized and cushioned knapsack, and you've got a wearable computer.

The showstopper, if there is one, in all of this is the display. Any kind of reasonable head mounted display is going to cost at least $1000, and could easily cost a lot more. Getting it properly configured could be a challenge as well.

For terminal based operating systems there are alternatives. For example, the Palm Pilot is capable of running vt100 emulation software, and making a terminal connection with a "host" computer via the Pilot Cradle connected to a serial port. If your laptop is running Linux, you can then run all your terminal based apps off the Palm Pilot. This puts the full power of a workstation literally in the Palm of your hand. This is easy and inexpensive to implement. However, you give up graphical display capabilities with this approach (though there are some interesting options using one of the Palm Web browsers and putting a Web server on the Linux machine).

For Apple laptops things seem a bit more problematic. I don't know if it is even possible to run much of MacOS off of a command line interface. My hunch is there ought to be some way to write code to export HyperCard displays to the Palm Pilot, and thus use HyperCard as your interface to the OS. You'd then have something like a HyperCard Wearable Computer. This would be pretty cool, actually. But I just don't know how feasible it is, since I don't know enough about the Mac.

Anyway, it seems clear that the path of least resistance to wearables is by starting with a laptop as the base platform. Costs have come down enough to make this a good balance of economy of time and economy of money.