Metronomics does not collect any personal data. There is no communication by default from the app to servers owned by Metronomics or any other service.
The saved files generated by Metronomics are stored on your device by default. If you choose to export them to another service (email, messsages, DropBox, etc.), Metronomics does not take responsibility for the privacy of your information from those organizations.
Metronomics offers an In-App Purchase for an auto-renewable subscription. No information is collected by Metronomics during this process. The subscription can be managed via Apple's tools.