Intoxalock, a Des Moines-based company, dominates the ignition interlock device market for drivers convicted of DUI. These devices require users to blow into a tube before starting their vehicle, measuring alcohol levels against state legal limits. Some states also track GPS location and take photos during each test.

Drivers lease these devices for $70–$120 per month, making them a significant ongoing expense. The system doesn't stop monitoring once the car starts. Intoxalock devices generate random retests during drives, giving users 3–15 minutes to pull over and pass another breath test.

If users ignore or fail a random retest, their horn and lights may activate as a warning. Depending on state regulations, drivers could face temporary lockouts. These devices create a constant surveillance system for DUI offenders, turning everyday driving into a monitored experience.