I might have this wrong but aren't you required by law - in France - to have one of these? That is even if you are a tourist. That's the only selling point to me, if I ever go to France. Then, I am tee total and I don't think that is useable as an excuse either....
Wait..I found it:
Since April 2013, carrying a breathalyzer with you in the car has been obligatory in France... by law - at least in theory. BUT this is a wonderful law that you are free to observe or not observe, as there is no penalty for drivers caught without a breathalyzer in their car.
Single-use certified breathalyzers are now available in many supermarkets, chemists and garages throughout France, at a cost of about 1 €uro each. So the cost is minimal.
Contrary to information posted on some sites, the new law (Decree no 2012-284) does not oblige drivers to self-test after having a drink. But those who plan to self-test to be on the safe side should have at least two breathalyzers in the car, if not more.
To conclude - breathalyzer or not - don't drink and drive. And remember that the tolerated blood alcohol level in France is 0.5 mg. per ml - just over half the limit tolerated in the UK (0.8 mg per ml).