Yes, most cycle tracking phone applications rely on outdated, calendar based, counting days since last menses algorithms. Learning to identify and chart biomarkers ensures women know where they are within their cycle on a daily basis. Several NFP methods offer cycle tracking phone applications that involve charting the biomarkers on electronic charts, allowing couples to make family planning decisions based on the actual biomarkers and not algorithms.

https://www.jabfm.org/content/29/4/508.full