The most impressive examples, and the most frightening, reflect the integration of geographical information systems (GIS), the Global Positioning System (GPS), and wireless telecommunications. A tracking device can instantly report its location to a GIS that determines whether the person, car or ship under surveillance has entered a prohibited area. Depending on circumstances and severity, a future system might be able to debit an offender's bank account, transmit a vocal warning or electronic pinch, notify the police or military, disable an engine, or even release a soporific drug into the violator's bloodstream.