Wearable computing facilitates a new form of human–computer interaction involving a small body-worn computer (e.g., a user-programmable device) that is always on, always ready, and always accessible. In this regard, the new computational framework differs from that of hand-held devices, laptop computers, and personal digital assistants (PDAs). The "always ready" capability leads to a new form of synergy between humans and computers, characterised by long-term adaptation through the constancy of the user-interface.

A wearable computer is a computer that is subsumed into the personal space of the user, controlled by the user, and has both operational and interactional constancy, i.e., is always on and always accessible. Most notably, it is a device that is always with the user and that the user can use while walking around or doing other activities.