(Photo : GettlyImages/ ROBYN BECK ) Fitbit smart ring Fitbit has officially applied for a U.S. patent on a smart ring that would track the user's blood oxygen and blood pressure levels using medical-level sensor technology. The smart ring is rumored to be Google's answer to the smart ring offered by its rival, Oura. Fitbit Smart Ring Patent Most wearable devices use reflected light to measure the user's blood oxygen. Still, Fitbit wants its ring to behave like a clinical pulse oximeter that passes light through the skin to a photodetector, according to Wareable. The process can help reduce the noise produced by the detector, and it can also improve the accuracy of blood oxygen measurements while making it feasible to track blood pressure and sugar levels.