Every morning Kayla Strata takes her temperature using a basal digital thermometer and checks her cervical fluid. She then enters those readings into a smartphone app to determine where she is in her monthly cycle.

Known as the Fertility Awareness Method (FAM), this is a way to track ovulation to either help a woman become pregnant or prevent a pregnancy. Strata started using this method in 2014 when she decided hormonal birth control was no longer an option for her because of its side effects.

“You have to be disciplined, but I’m so passionate about this that I follow it diligently. I’m part of a group of women who use this method, and they have been able to avoid pregnancy for years,” she says.

Before the contraception pill, women regularly used FAM, or rhythm method, as a way to prevent pregnancy. And until recently this method meant keeping a paper trail of a woman’s monthly cycle data.

Now the tech scene has taken note and is helping women understand their monthly cycle with smartphone app charts, including ones from Selene, iCycleBeads and Groove. Strata uses the smartphone app Kindara, which, according to its founder William Sacks, has had 700,000 downloads and is just as effective as hormonal contraceptives.

This year Kindara introduced a Bluetooth Wink basal body thermometer that automatically syncs with the Kindara mobile app. “People have an intimate relationship with their smartphones, we have so much information on them, and this is some of the most intimate information there is,” Sacks says.

According to Sacks, Wink is four times faster than other basal body temperature products on the market. Women are encouraged to keep Wink by their bedside and take their temperature as soon as they wake up. If they forget, Wink will vibrate to remind them.

“If your oestrogen level is low, you’re good to have unprotected sex and have a zero percent chance of getting pregnant. Or, if your oestrogen level is high and rising and you want to get pregnant, today would be a great day,” he says. Eventually, he says, a woman will be able to look at her smartphone to determine their hormone levels with sensing technology.

“In ten years this will exist. I’m not sure if it will be an implant, patch or clothing based sensor, but women will know what is happening every day, with no confusion about their fertility,” he says.

Chantae Hergenroether used the data to help her get pregnant. She had been receiving Depo-Provera injections, but when she decided to start a family she found out it would take up to two years for the drug to leave her system.

“My doctor told me not to plan on getting pregnant for at least a year,” she says. From there she searched the internet to see how she could improve her chances of becoming pregnant faster, and decided to track her cycle digitally.

Using the technology forced her to become “baby focused”. Taking her temperature first thing in the morning reminded her to make healthy choices in her diet and to exercise. Doing this she became pregnant within two months of coming off the injections.

“This is bringing technology into something we’ve known about for a long time,” Dr Helen Webberley of the Oxford Online Pharmacy says. According to Webberley, anyone who uses this method will automatically understand their menstrual cycle, and for motivated women who have regular cycles, it can be an effective method of birth control.

“If you went up to someone on the street and asked them if they knew that there’s a completely natural way, without hormones, coils, condoms or diaphragms, to avoid pregnancy, they wouldn’t know it,” she says.

In addition, Webberley says that learning how to track your cycle can also help a woman understand why she’s not getting pregnant.

“If you’re doing a family planning cycle and you’re not getting a rise in basal body temperature, you can tell your doctor that the reason you’re not getting pregnant is that you’re not ovulating. So rather than using expensive fertility treatments, there’s a tablet called Clomid that will make you ovulate.”

However, she warns that if you take paracetamol or have a drink, your basal body temperature can be affected. “If pregnancy would be a complete disaster, maybe you should think about using another method,” she says.

Fertility tracking is only one way people are tracking their health. In the UK, 13.1 million people will use a health tracker in 2015, up from 6.7 million in 2014, according to Kantar Media.

The NHS has a website explaining how to use trackable devices and apps for health issues such as how to quit smoking, lose weight or improve a diet.

In the US, 69% of adults keep track of their health, such as blood pressure, diet or headaches, with 21% of them using technology to help them do so, according to the Pew Research Center.

Jennifer Daskal decided to use a wearable device to track her second pregnancy. Living in the tech hub of San Francisco, California, she hears about many health tech devices, so when she was approached by Bloom Life to track the third trimester of her pregnancy she decided to give it a try.

Set to be approved by the US Food and Drug Administration in 2016, The Bloom Life device is a small sensor that sits below a pregnant woman’s bellybutton. It picks up on motion and electrical activity within the mother’s body. The motion is an accelerometer, like a FitBit, and measures activity such as walking, running and sleeping, while electrical activity measure organs, such as the mother’s heart, the baby’s heart or the uterus.

“Collectively these signals from the mother and the baby are the most important health parameters that doctors care about to determine whether or not the mother and baby are healthy during pregnancy,” Eric Dy of Bloom Life says. Once this data is collected, it is then transferred to the mother’s smartphone so that she can track fetal movement and contractions.

“For first-time mothers trying to track some of these things is guesswork. This is a way of tracking these parameters without the mother doing anything. The sensor will automatically track this information, send it to a smartphone, and then the woman can share it with whoever she wants.”

By wearing the device, Daskal felt she understood her body better. “When you’re pregnant for the second time, you’re better prepared, but for me it was more about visually seeing what I was experiencing.”

What she learned was that she was having several contractions that she wasn’t feeling.

“I felt like I was really far away from labor, but because of the device I could see that I was having contractions that I wasn’t feeling and that my body was preparing.”

However, Daskal understands that women feel pain differently. “You could be like me, and not feel your contractions, or you could feel them a lot, so you can see how strong they are – are you feeling them strongly? – or maybe your pain threshold is lower.”

Bloom Life also has the ability to pull data from third-party devices. “If you’re diagnosed with gestational diabetes or pre-eclampsia, the mother is told to record her blood glucose levels or blood pressure twice a day. We can collect that data from these devices to provide a much more objective measurement because it can tell you what you were doing when you took your blood pressure. Was it up because you were walking up a flight of stairs, or was it up because of your hypertension?” Dy says.

However, Dr Maureen Baker, Chair of the Royal College of General Practitioners, warns women about investing in technology devices during pregnancy.

“Conditions such as gestational diabetes and preeclampsia are extremely worrying for pregnant women, but the best care, advice and support are available from qualified health professionals, free of charge on the NHS. We cannot comment on the effectiveness or reliability of this particular device but we are concerned that some mobile phone apps, which are promoted as providing greater reassurance to patients, can actually cause unnecessary anxiety and this is particularly worrying for women in the later stages of pregnancy.”

Baker says that mobile phone apps and medical devices have huge potential to support patients and the health professionals who provide their care – but only if there is credible evidence to support their claims.

It is worth remembering that no device is 100% reliable and if you are paying a significant amount of money for a product, it is important to check that it meets the required standards, and is CE marked or equivalent.

“We would advise any woman who has concerns about her pregnancy to speak to her healthcare professional before spending money, unnecessarily, on something that might not work.”

• This article was amended on 22 July 2015. An earlier version referred to progesterone where oestrogen was meant.