I am working on a Kivy app for iOS and Android and need help with keeping the user persistently logged in, even after the app is closed or killed. I am using Parse to store user
The answer is essentially that you must simply save the data somewhere. The details will depend on your requirements, and aren't specific to kivy - you can look up normal android or python practices.
I'm not sure exactly what android guarantees about permissions, but storing stuff in your app directory (on the main partition, not 'external' storage) should be inaccessible to other apps, though anything with root can view them. You can use normal python tools if you want to encrypt the data, and manage your own kivy gui for getting a decryption key/password from the user.