Ignition interlock devices are often ordered for people who have been convicted of one or more DUIs in order for offenders to get their driver's licenses back. IIDs are essentially Breathalyzers connected to the ignition that determine whether drivers have alcohol on their breath. If they do, their vehicles won't start.
States that require IIDs for all people convicted of DUIs have seen a significant reduction in drunk-driving fatalities. Some 22 states require them for even first time DUI convictions.