Create device similar to shopkick

I want a device similar to what ShopKick That produces a high pitch sound that can not be heard by humans. Specifications: -Sound must be coded with a unique sound code that will be picked by smartphones, each device must have a unique sound code. -The device must cover large spaces with obstacles and noise. -The device must produce high pitch sound with more than 21khz that cant be heard by humans -I will need the demo device to be shipped to my country. -I will also need the documentation to reassemble this device and circuit design. -220v plugin input. - The most important thing to keep in mind is that the device components and assembling cost must be as low as possible(for later production).