A customer uses the Scan It! Mobile app on her Android phone to scan groceries at the supermarket. Retailers are in the midst of the technology revolution. Research firm VDC Research estimates retailers worldwide will spend 12 percent more on installing self-check-out kiosks -- which require fewer staff -- by 2015. Outlets are piloting the program that allows shoppers to use their smart phones to scan groceries as they pull them off the shelves -- a move that could lead to even fewer check-out clerks.