We’re thinking of getting an ovulation testing device would this be an effective birth control method?

My husband and I are opposed to using the Pill or other contraceptives, but we don’t want any more kids. We’re thinking of getting an ovulation testing device (a really expensive one that tests saliva and vagina conditions and charts the results on the computer), and then ONLY have sex three days or more after ovulation occurs.

If we’re very careful about sticking to this plan, would this be an effective birth control method?