Electronic tagging is a form of surveillance which uses an electronic device (a tag) fitted to the person. It is commonly used as a form of electronically monitored punishment for people who have been sentenced to electronic monitoring by a court, or required to wear a tag upon release from prison. However, electronic tagging and monitoring is also used in healthcare settings with people with dementia and in immigration contexts in some jurisdictions. If the device is based on GPS technology, it is usually attached to a person by a probation officer, law enforcement or a private monitoring services company field officer, and is capable of tracking the wearer's location wherever there is the satellite signal to do so. Electronic monitoring tags can be also used in combination with curfews to confine defendants or offenders to their homes as a condition of bail, as a stand-alone order or as a form of early release from prison. The combination of electronic monitoring with a curfew usually relies on radio frequency (RF) technology, which differs from GPS technology.
The use of home detention as a means of confinement and control within the home can be traced back to biblical times when the Romans placed Paul the Apostle, under house arrest.
In the 18th century, the English philosopher and social theorist Jeremy Bentham designed the Panopticon, a hypothetical prison. Inside the Panopticon (the name is derived from the Greek word for "all-seeing"), the prisoners are arranged in a ring of cells surrounding their guard, who is concealed in a tower in the center. The idea is that the guard controls the prisoners through his presumed observation: they constantly imagine his eyes on them, even when he's looking elsewhere.
"[T]he persons to be inspected should always feel themselves as if under inspection ... for the greatest proportion of time possible, each man should actually be under inspection."
Bentham promoted the concept of the Panopticon for much the same reasons that spur criminal-justice innovation today—a ballooning prison population and the need for a cheap solution with light manpower demands. It is worth remembering that when the modern prison emerged, it, too, was promoted as a reform a positive replacement for corporal or capital punishment. Early prison reformers—many of them Quakers bent on repentance and redemption—suggested that cutting people off from the rest of the world would bring them closer to God. (The word "penitentiary" comes, of course, from "penitence.") Whereas the guard in Bentham's day had only two eyes, however, today's watcher can be virtually all-seeing, thanks to GPS monitoring technology. The modern prisoner, in other words, need not wonder whether he is being observed; he can be sure that he is, and at all times.