A natural user interface (NUI) is computer interface defined by how a user interacts with it, i.e., naturally, without the use of a keyboard or mouse. You’ll often hear of the interface being “effectively invisible.” For you science fiction fans, think Minority Report gadgetry (except for the time travel stuff).
Natural user interfaces are being developed to recognize
Voice
Fingerprints
Gaze vectors
Facial expression
Handheld device movements
Biometrics such as heart rate, temperature, pupil size, body temp, heart rate, and even sweat (aka skin impedence)