Had to have a Guardian device installed for 6 months. First month, everything went fine. Then during my first check in, they said the software in the device wasn't working correctly so they gave me a new handset. From that time on, it never worked correctly and would "abort" almost every time that I tried to blow into it. Had my car towed to try to get the issue figured out and they continually told me that I was the issue, not blowing in correctly (even though the first month I had no issues at all). Had about 4 different handhelds and none worked. So about 2 months in, decided to not even try driving because it wasn't worth getting a potential violation from too many tries and it not working, so took cabs everywhere. My advice would be to look for alternatives (or just not drive) rather than go through the emotional and financial troubles I experienced.