GPS ankle bracelets track offenders
As this USA Today article explains, "the GPS units typically consist of a small, lightweight ankle bracelet and a personal transmitter unit, or PTU, worn on a shoulder strap or around an offender's waist. The system sends an alert if the ankle bracelet is not within a prescribed range of the PTU, which is in constant signal contact with a network of Department of Defense navigation satellites orbiting 11,000 miles above the earth."
One of the things law enforcement folks love and bad guys hate about this use of GPS is that "it can pinpoint a wearer's exact location, rather than just alerting a probation officer that a subject [on probation or under house arrest] wearing an RF ankle bracelet has strayed from the base unit."
You are so busted.