Finally, there is the processor. In a fifth generation system, typically the processor is a small laptop computer, notebook computer, or the like, worn in a satchel, belly bag, backpack, or otherwise attached to the body in some way.

In a sixth generation system, the processor is typically a small single board computer, that can be put into a small metal box. This setup is a favorite among hobbyists, because of its flexibility and ease of interface. For example, a 64 pin ribbon cable can be attached to the Industry Standard Architecture (ISA) bus of the computer, and connected to a small solderless breadboard in the system.

Traditionally, one of the problems with wearable computing, is that the wearer tends to look unusual. Owing to this unusual appearance, people used to call me "computer Steve." Like any new invention, the early prototypes often look silly by today's standards.

The computer itself can be made quite small. For example, in a seventh generation system, the components are distributed and concealed in a structure similar to an athletic tank top, for being worn underneath ordinary clothing. This structure also allows the device to pick up physiological measurements, such as respiration, heart rate, and in fact full ECG waveform. Electrodes on the inner surface of the device pick up signals from the heart. For best reception, I usually clear away some of the hair around where the heart is, or, more generally, clear my entire chest area entirely of hair, rather than having a dozen or so "holes" where hair is missing. It is common, for example, among swimmers, to clear away all body hair from the neck down to reduce water resistance (to increase speed), so clearing away a portion of the body (such as the chest) will not seem so unusual as it might sound. Alternatively, or additionally, electrode paste can be used on the chest to improve the quality of the measured ECG waveform. A modular system allows electrodes to be moved around for simple experimentation.

Alternatively, when it is not necessary to collect physiological data, we sometimes use small size commercial off the shelf computers, such as the Expresso pocket computer, which can fit in a shirt pocket, and be concealed underneath ordinary clothing, without too much difficulty.

Batteries can be distributed and are easy to conceal, so that, in and of themselves, the appearance will not be unusual.

As mentioned above, the display device is, perhaps the most important characterizing feature of the WearComp. Thus you will no doubt want to consider building a covert display system.

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