Add a new feature to the app that can read bank transactions
I like your app so much that it provides sophisticated charts along with expected outlook expense. We can link bank account but may be some people think there might be security issue or bank sync may not work properly all the time.
So create a new feature in your app so that it can read all credit and debit messages from the bank whenever we do some online payments. This can also read bank name in the messages. Then it can create an automatic expense or income record for particular bank account.
This can help you with syncing problems with server. People wont be worried about their money, more people may install your app.