Larry Edsall:

A variety of automakers equip their cars with a dial so the driver can select from normal (touring) or sport or in some cases even track-mode settings, or in the case of sport utilities, the settings may be for winter driving or even various off-pavement environments. Such settings adjust engine computer controls, transmission shift points, or even how soon and how aggressively the traction and dynamic vehicle control systems kick in.
 But Roush Performance has devised an aftermarket exhaust system that not only can be dialed into touring, sport and track sound levels, but even to a custom setting that uses a smartphone or tablet app that enables the driver to achieve a seemingly unique sound — or a series of such sounds — for his or her vehicle, and even to link the various sounds to a phone’s GPS system