It appears that Google has started quietly pushing a major change for the Pixel Watch, eight months after its launch. As we noted in our review, Google had not enabled the smartwatch's blood oxygen (SpO2) sensor, despite referring to the sensor's inclusion in official technical specifications. Instead, the Pixel Watch offered estimated oxygen variation (EOV), an approximation of blood oxygen saturation level changes.
As the screenshots below show, Google has started enabling the smartwatch's SpO2 sensor, but its functionality remains limited. Supposedly, it is only possible to view blood oxygen saturation levels for when you last slept. In comparison, recent Apple Watch models read blood oxygen levels every few hours and can also do so on demand. For reference, you can see whether your Pixel Watch is now monitoring blood oxygen saturation levels by navigating to the 'Oxygen saturation' card within the Fitbit Today app.
Currently, it is unclear how Google is enabling this new feature, which it did not bundle in this month's software update. Likewise, Google has not pushed a new version of the Fitbit app, either. Potentially, Google has introduced full SpO2 sensor functionality by a server-side change, although it has not provided any details yet. At any rate, it seems that Google is preparing to unlock SpO2 functionality for all models soon, reputedly just one of several fitness tracking improvements headed to the Pixel Watch platform later this year with the release of a Pixel Watch 2.