There should be some iOS-specific system with a key in protected keystore/keybag on the phone, combined with your encrypted password db potentially living in dropbox/icloud/etc., and then a user passphrase or biometric or whatever to unlock the file. Then you at least are protected against brute force once someone steals the encrypted keyfile from dropbox or some other service.
I've suggested this to them ~10 times. A keyfile format that doesn't rely on the crazy Apple resource forks and works with a user-self-hostable sync server would also be nice.