The best way to start with sixth sense is to get some background in 'Image Processing'. Matlab is a great tool for this. This video is somewhat mid-range, assuming that you have a decent background in computer programming. If you don't, then you can find similar videos for beginners on youtube.Since Matlab runs on a computer, you don't need a smartphone. It simply takes inputs from a webcam and processes it.If you want to implement sixth sense as a standalone device ..you'll have to use a microcontroller like arduino which takes care of the computation.