The visual tracker detects and tracks corner features in the view of your cellphone camera. The tracks of individual features are shown as tails to the current location of the feature. The tails is colored according to how old the respective position is relative to the current position: From very recent observations in yellow to old corner positions in red.
The application has the purpose of demonstrating some of the state of the art Computer Vision and to be fun to play around with (How long can you keep a feature tracked while moving your cellphone around?).
The OpenCV library for android is used for feature extraction (FAST features). See the documentation webpage http://www.j-robotics.com/visual-tracker/ for more information and and the BSD license of OpenCV.