MyMobileAlert tracks the cellphone via GPS as its owner drives about their business. When the system determines the chatty driver is approaching within one hundred feet of a stoplight or a certain distance from an intersection, the cellphone will emit a loud 'chirp' to notify the driver who can then take any appropriate actions.
The only requirement for MyMobileAlert is a GPS-capable cellphone; the issuing wireless company would install the necessary software. So far the system has been demonstrated in cities such as West Hollywood, California.
[Source: Technology Review]