An ignition interlock device is installed on a vehicle, and requires the driver to blow into a tube that detects the presence of alcohol. If alcohol is detected, the car will not start.
This device is quite expensive, costing approximately $100 per month plus a heavy insurance surcharge, and requires you to have it inspected once per month at an inspection station, regardless of whether or not you have a license. So it’s a major hassle.
It’s imperative you consult an experienced attorney, because in a first-tier DUI, there is some leeway regarding whether or not the court will impose installation of the device.