The sensor on Grove - Gesture is a PAJ7620U2 that integrates gesture recognition functions with general I2C interface into a single chip. It can recognize 9 gestures including move up, move down, move left, move right, etc with a simple swipe of your hand.
You can use the gesture to adjust the sound volume, control a robot. You can also make a remote-control unit, which is able to operate many devices at the same time using gestures.
Features
9 gesture recognition
Built-in proximity detection
Various main boards support : Arduino UNO/Seeeduino/Arduino Mega2560