(Pocket-lint) - Fitbit has finally started rolling out its blood oxygen tracking feature to several of its latest wearables. 

The feature is being enabled on the Charge 3, Ionic, Versa, Versa Lite and Versa 2, and will will allow users to keep track SpO2 (blood oxygen saturation). In short, you'll be able to an estimated amount of oxygen you have in your blood. 

It's a useful feature, and could help uncover breathing issues in people who have them without knowing. 

By tracking it throughout the day, you'll be able to monitor any big fluctuations in your blood oxygen saturation. 

Of course, Fitbit isn't the first company to offer SpO2 monitoring in its wrist-worn fitness gadgets. Garmin's watches have featured a Pulse Oximeter (Pulse Ox) tracker for a little while now, but Apple is yet to enable the feature in its own smartwatches. 

It's yet another impressive capability being added to the smartwatch and fitness tracker market, and is indicative of a general move that allows consumers to personally monitor some important vitals we used to have to go to the doctor for. 

Take Withings' latest device - the ScanWatch - which adds SpO2 monitoring alongside irregular heartbeat, Afib, possible sleep apnea detection and an ECG scanner. 

It's clear then that all of these popular smartwatch and fitness tracker manufacturers want to do more than just count our steps and work out how many calories we're burning. They're shifting into being all-round health monitors. 

According to CNET, Fitbit has started rolling out the new SpO2 tracking feature via a software update this week, so if you have one of the devices mentioned, be sure to check for updates. 

Writing by Cam Bunton.