The device will be checked monthly and it will cost the offender about $1800 over the 12-month period.
Any attempt to tamper with the interlock, or to start the engine by bypassing it, will be recorded in the device as a violation, as will any readings of excess alcohol.
The system covers most bases but, as some critics have pointed out, it is not fool-proof.
Offenders can still get access to other vehicles or, potentially, get a sober associate to blow into the device for them.
Some motoring watchdogs, while supporting the scheme, have also pointed out that it does not address the underlying addiction issues of repeat drink drivers. One has gone as far as saying it won't work on the highest risk offenders because the cost is prohibitive.
The AA believes interlocks should be mandatory for repeat drink drivers or those caught with extremely high alcohol levels.
They have a point but, given the complexities of issue, a pragmatic approach is needed.
Interlocks are a good step forward in reducing carnage on our roads. In time, these devices may well become mandatory for recidivist offenders but, for now, they are a start.