Show me where you store the data.

If you store it on your phone, then it's not showing up on your other devices. If you lose or break your phone, then your data is gone. There are very few applications for which that's acceptable - basically just your calculator app.

If you don't store it on your phone, then it's stored on some kind of server, somewhere. Do you own and control that server, or does someone else? How does the application consume and update the data?