Ultrahuman's new fertility tracker is nearly a Natural Cycles dupe - but it's free to use

Nina Raemont/ZDNET

One reason Oura has gotten so popular over the years is because of the smart ring brand's partnership with FDA-cleared Natural Cycles, a non-hormonal contraception app that tracks fertility and costs $100 a year. 

Underdog smart ring brand Ultrahuman just introduced a fertility tracker that could rival Oura's partnership. The best part? It's free to use with the smart ring. 

Ultrahuman recently announced its Cycle and Ovulation Powerplug, a feature that Ultrahuman Ring Air users can unlock through the app. The Powerplug uses data collected by the smart ring -- like skin temperature, resting heart rate, and heart rate variability -- to offer information about the user's ovulation, seven-day fertile window, and menstrual cycle. 

"Most fertility tracking today is either inconvenient, expensive, or both. Women often have to use two apps, pay for two subscriptions, and even purchase separate devices just to track their fertility," Mohit Kumar, founder and CEO of Ultrahuman, said in a release.

Also: The best smart rings you can buy

The Powerplug goes beyond tracking a person's basal body temperature, the key indicator used to track and determine a person's ovulation window. This newly introduced method for fertility tracking comes amid a flurry of "tedious" and "not the most accurate" conception planning methods, according to Ultrahuman. 

In its press release, Ultrahuman explains how the Calendar Method, Basal Body Temperature, and Ovulation Predictor Kits all come with different hurdles that are either inaccurate, inconvenient, or difficult for long-term planning. 

The smart ring identifies key phases of a person's menstrual cycle, like the menstrual, follicular, ovulation, and luteal, and displays this information with insights into each. 

The fertility tracking feature also takes a person's age, BMI, skin perfusion, and diurnal stress into consideration while monitoring and predicting an ovulation window, which increases accuracy and takes the cycle variability into account, according to Ultrahuman.   

Also: I tested a subscription-free smart ring that rivals Oura

The Cycle and Ovulation Powerplug isn't a direct duplicate of Natural Cycles. For one, the Ultrahuman fertility tracker hasn't received FDA clearance, so it can't be used as a confirmed form of contraception. 

What this new feature does prove, however, is the fact that Ultrahuman is making strides to directly compete with Oura and its partnerships by offering up similar products at a cheaper – or completely free – price tag. The brand is claiming over 30% of the smart ring market share, according to a recent press release. Earlier this year, the brand only held 10% market share.