IMO I am not controlling his drinking, I am controlling whether our family's cars will be used in a DUI and trying to limit my legal responsibility in the case of him getting a DUI or worse, harming someone else. The only other way I know of doing this is divorce, and I am not there (yet?).
I know legal consequences do not change their behaviour. He had driven drunk. He picked me up from work and I did not immediately realize he had been drinking. Until that point I believed he would not drive drunk. Well, he was so drunk he went by our house and went a good two more blocks without realizing it.
The worry of what he could do driving drunk, for me, was worse than the worry about him being alcoholic, including what I know about me and kids being hurt/codependent. I was terrified he could hurt/kill some innocent people as well as himself.
I am sure he resents the breathalzyer being on his car. I am sure, too, he would hurt terribly if he harmed someone else. I am sure he would also resent it if I let him leave driving drunk and then called the police on him.
If he wants to drink and get around he could always do public transportation. He chooses not to and to control his drinking so he can drive when he feels he needs to, mainly just to and from work and the odd errand Saturday morning. We don't pick up the slack if he can't start his car, because we feel that's a consequence of drinking that he should face.
For me, and my kids agree with this situation, the breathalyzer is the best option we have to prevent his drunk driving and for us, this works. I/we can sleep nights.
Anyways....take what you want and leave the rest. I've gone on too long about this so I'm jumping off my soap box. (Now, there's a phrase that dates me!)