The original Fitbit was designed to clip onto pants or running shorts, but in recent years the company has devoted its design to smartwatches and best fitness trackers. However, according to a recent patent, the company is now exploring the possibility of a smart ring.

What makes this patent interesting is that it suggests that the ring would not replace existing wearables, but augment them by measuring blood oxygen saturation (SpO2) with a built-in optical sensor.

This could be much more accurate than wrist-worn solutions such as Fitbit's current fitness tracker. In fact, the form factor of the ring is similar to a pulse oximeter used in clinical settings, which clips onto a finger and passes light from one side to a light detector on the other. Since oxygenated and deoxygenated blood absorb light differently, the SpO2 value can be determined from this measurement.

Wrist wearables are different. The wrist is obviously thicker than the fingers, and wearable technology does not typically wrap around the wrist. Therefore, SpO2 sensors in fitness trackers use reflected light instead. Therefore, the SpO2 sensor in the fitness tracker uses reflected light instead. This gives an approximate value, but is not as accurate as a dedicated pulse oximeter.

According to the patent, the ring passes the collected data to a cell phone or Fitbit wearable via Bluetooth or NFC. Importantly, Fitbit mentions the possibility of a motion tracker on the ring. This is not to count steps, but to make sure the wearer is not moving around, which would not be accurate. The patent states that "motion sensors can be used to remove noise from the data due to motion."

Smart rings for health management are not new; Oura also wears one on its finger and measures sleep, steps, heart rate, and temperature deviations. And recently, the NBA bought 2,000 of them for its players and staff to record metrics in its battle against Covid-19, giving them more credibility for their health.

But the Oura is a $300 smart ring, and Fitbit's may have to be significantly cheaper to be attractive.

And of course, there is another major assumption here. But with Google as Fitbit's new owner, the company certainly has the budget to try new things.