Currently, Cardiogram accesses data from Google Fit and makes it more engaging and actionable to users. Cardiogram reads data from (rather than writes to) Google Fit. 

In the future, we want to make it possible to write data back to Fit, and our dedicated engineering team is already looking into how to make this happen. The good news is that Google is making significant changes to their API as part of their upcoming version of wearOS, and these changes will make it a lot easier for data from apps like Cardiogram to end up in Fit. The bad news is that it’s unclear when these changes are going to be released for each brand of wearOS device, so we can’t currently provide a definite timeline on when to expect this feature in Cardiogram.