This paper presents the Button Keyboard, a very small wearable keyboard with universal usability. The Button Keyboard has high wearability and social acceptance due to its remarkably small size. As it is roughly button sized (33mm×33mm), it can be worn on the body without any discomfort. In addition, it adapts a mobile QWERTY layout to improve text entry for general users without special training. After an evaluation of the text input performance, it was found that the keyboard provides sufficient text input speed and learnability in spite of its small size. Furthermore, a touch-sensitive keypad divides input states by recognizing finger motions. Therefore, the system can provide visual or auditory
to users. Thus, users can confirm the key before they execute. This previewable feature makes the keyboard a highly usable example of a wearable computer, in that it reduces the focus of attention and frequency of error. Moreover, it has the potential to assist the disabled by providing effective and appropriate ranges of feed-forwards.