Sample: I would eliminate the need for a physical card an opt for some kind of biometric id such as a retinal scan or some such. I would orient the display to eliminate the opportunity for over lookers to view it - i.e.. make it horizontal like a table. I would eliminate the masking of account information behind names such as checking, savings, etc. and ensure that at least the balances are always displayed. This would help eliminate a good deal of you dont have enough funds-type msgs. Add an Undo capability where appropriate, i.e. for transfers/deposits. It would also negate any costs associated with the original transaction. Remember the most common transactions done by the user and make them macros automatically.