Rhythm method of birth control has been practiced and promoted by Catholic church for many years.The principal is that a female is able to get pregnant for only a few days a month.These days are limited to only 3 to 5 days a month.That is the period woman is ovulating.Catholic church teaching helps one to figure out the ovulation period by counting the days from a mensuration cycle.
Normally woman is fertile ( ovulating ten days before mensuration) so it depends on charting the menstrual cycle and predicting fro it the most fertile period and then regulating sex in that period for getting pregnant or not.
Why it is needed:
Currently most common method of female birth control is Pill( estrogen).This is a daily hormone dose to have higher level of hormone which fools the female body to think it is already pregnant and as such protect it from going through another pregnancy.Other methods are slow release of hormones by an implant and cervical ring.Ring has to inserted by doctor or a Practitioner which is not very practical and expensive in the west.The chemical methods( hormones) create problems for many women and leave them bloated and dis comfortable.None of these methods help women know there fertile time for the ones who want to have children.There is a need of non chemical method of detecting fertile period of women for birth or avoidance of it.
Biology of it.
If a female takes daily basal temperature and it is tracked and charted .this temperature goes up by .5 degrees during the period a woman is ovulating.By choosing to or not desired results in pregnancy can be had.
To build a Digital memory thermometer with visual and sound alarm .All would be required is for female to check daily temperature and when the temperature is .5 degrees higher alight will go on and a beep will be heard .This will be a signal that female is ovulating .it will give the choice of birth control in the hands of patient. A chart can be transferred to a smart phone for further analysis if needed.Specialist could be developed to analyse this data or this data could be sent electronically for analysis.