Ignition Interlocks

Increasingly common in the supervision of drunk drivers, ignition interlocks prevent vehicles from starting unless someone sober blows into a machine attached to the engine.

Polygraphs

Though controversial due to persistent questions about their accuracy, polygraph machines are a tool used by many supervision agencies. Polygraphs are used most often with sex offenders in attempt to discover whether they have been involved in any prohibited activities, since such activities are otherwise difficult to detect.