Many a times it is a tough call for referees to pin point where the ball is in a turbulent game. A Carnegie Mellon University professor is working on a project to develop a "smart football" with a GPS device built into it to produce 3-D, real-time position readings that would help referees make the right call in determining the correct position of the football on the field of play. The "smart football" weighs 3.5 ounces more the NFL's limit. Second, the GPS doesn't work very well when the ball is in a spiral and it loses track of the satellite signal. Moreover, it's still a long way from being able to provide an accurate placement on, say, a 4th-and-inches play.

The current prototype transmits information once a second and is only accurate to within 30 feet - obviously not good enough for practical application. A newer prototype will transmit four times a second and will combine its data with information from fixed GPS receivers near the field to provide much tighter measurements.

Via