This document discusses gesture phones and gesture recognition technologies. It describes different tracking methods for gestures like optical tracking using stereoscopic vision and triangulation, and inertial tracking using a single camera and rolling shutter. Examples of using gestures to answer calls, browse the web, and control other devices are provided. Both the benefits and challenges of gesture recognition technologies are outlined, like the need for a flexible programming environment versus high power consumption. Potential future applications using ultrasonic waves and infrared are also mentioned.