The FDA has approved marketing of the first mobile medical application (app) called “Natural Cycle” which contains an algorithm that calculates the days of the month a woman is likely to be fertile.
Natural Cycles requires taking your temperature daily using a basal body thermometer, in the morning immediately upon waking, and enter the reading into the app. Also, tracks your menstrual cycle.
If you adhere to the app's directions perfectly, roughly 1.8% of women would become pregnant in a year.
For more information, see FDA press release