BPBliss provides a convenient way to enter simple health related data.
You can view your entered data with the App, but goal of the App is put the data in a normal Google Sheet that you are then free to analyze it graphically or statistically.
Once you revoke access permissions in BPBliss (or directly in Google's privacy section), the App has no access to the data is helped you input, but of course as owner of the data you retain access until you decide to delete it.