SoberLink has worked well for me. For $200 a month, the service provides unlimited tests weekly, and we scheduled two tests a day (you can opt for 2, 3 or 4 and set your own schedule of testing and acceptable windows - then the system texts or emails you each time a test is taken with the results).
Personally I wanted my ex to test daily because I think he is worse as a parent when he is dry and wanting to drink than when he is actively drinking, at least as far as the kids' emotional health is concerned.
During the period of monitoring, I was convinced that SoberLink kept him sober (rather than proving he was sober). As soon as he goes off monitoring, he slips / relapses, and the cycle begins again. We are about to begin another one, so it's not ideal. But I will say that it dramatically reduced my level of stress and gave me a level of confidence while he was monitoring, in part because having that level of accountability changed his behavior.