Best the enabling of the 2FA for logging into account and for transferring nxt.
If not possible then a pin for transferring money.
Option to lock your account to a trusted device so it can not be accessed from other device without your consent.
White label/black label list of accounts you allow or disallow to transfer nxt to.
Option to hide the amount available in the account while client is open.
The icon for receiving and money sent gives me the opposite impression. The icon i have sent money looks like i received money and the icon a received money looks like i have sent money.
address-book with addresses nxt has been sent to with a label.
History of transaction by address recipient, by date, by amount.
Columns with headers of the transaction amounts (Debit/Credit or Transferred/Received).
Send nxt in red or with - or within (xxx).
Not using the Fiat $ sign in front of the nxt
Having the nxt sign in front of your balance.
The above are off top of my head. Will have to delve deeper into the client to give more suggestions.