Location-based ubiquitous computing systems are entering mainstream society and becoming familiar parts of everyday life. However, the settings in which they are deployed are already suffused with complex social dynamics. We report on a study of parole officers and parolees whose relationships are being transformed by location-based technologies. While parolees are clearly subjects of state discipline, the parole officers also find themselves subject to new responsibilities. This study highlights the complexities of power in sociotechnical systems and what happens when location becomes a tradable, technological object. Author Keywords Discipline, Power, Surveillance, GPS. ACM Classification Keywords H5.m. Information interfaces and presentation (e.g., HCI): Miscellaneous. General Terms: Human Factors.