embedded project

hello i am in my final year engg and i wish to do project on embedded 
systems.
i need to develop an application 'smart atm using gsm' to interface arm 
processor lpc2138 with an lcd, 4*4 matrix keypad, gsm transreceiver and 
all the coding is to be done in c++ or assembly language.
in this project user can withdraw money from atm without his atm card, 
he will get two options at atm machine 1:with atm card
2:without atm card
if he chooses 1 option the procedure will be same but if he chooses 2 
option he need to enter an unique id and password to access the account 
then the system will call to registered account holder and ask for the 
permission whether to allow the person to access the account or not. if 
the account holder denies he wont be able to withdraw money but if he 
allows then user can withdraw money.
please help me out with interfacing diagrams and code.
thanks .
gaurav singh