I discovered quite by accident an easy way to stop a drink driver from drink driving. You can buy for about $20 these days a cordless doorbell for your home, which consists of a transmitter unit and a receiver unit.
The transmitter unit, while transmitting, prevents the use of the device on your keyring. Hence you either can't open your car or you can't start your car. (Provided the car is fitted with suitable alarm / immobilising equipment.)
You can stick the button down and blutack it somewhere on the car's body. .Within 24 hours the battery should go flat so you can drive your car away, or you can just switch it off when the person has sobered up.
Range of transmitter is about 10 to 20 metres.
Now, back Home.