Objective: To show the effectiveness of cycle applications in both areas of application—contraception and intended pregnancy. Methods: A systematic review based on the PubMed and Google Scholar databases, with the addition of a hand search, was conducted from May 11, 2023, through April 11, 2024, to objectively answer this question. Of 1539 sources with matching search terms, 19 sources remained after checking for inclusion criteria according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses scheme. These were analyzed according to an evaluation scale regarding their quality in various areas. The average quality ratings and pregnancy probabilities of the studies were compared. Results: Comparability within and between the subquestions was hardly possible owing to different presentation of results, bias risks, and mostly uncontrolled study designs. Applications for those wishing to become pregnant provided better quality ratings in some cases. There were indications that cycle applications shorten the time to achieving a desired pregnancy in cases of reduced fertility. In addition, some seem to have a similar contraceptive safety as the contraceptive pill but require significantly more compliance. Conclusion: Independent, controlled studies with a diverse clientele of test subjects are necessary for a scientific classification. In addition, social, structural, and political adjustments are needed to enable individuals to make informed decisions about the use of cycle and fertility applications.