You have two providers in your state that have reliable devices. Please read the forums to get a feel for the devices and how to use them.
You should not let the car just sit with it on because then to them it looks like you were driving something else because it records how many starts and stops of car. Plus, When you go in for your check-ups they will record the mileage. If you are not going to drive at all then I would suggest just not getting an interlock and filling out the option that you are swearing not to drive. They had that option in my state of IL.
Also, I would get rid of your attorney. Sounds to me like he is trying to instill fear into you.