interest calculator clock

Im looking for someone to develop an android and Apple app for me which will calculate and show interest earned in real time CLOCK. I wish the user to be able to input a dollar amount, day of the month to add amount and an interest rate. the same dollar amount will be added each month on the day given. then the app will calculate the interest every second and update the total amount (input dollars and interest) in a real time clock method. The app must always run in the background do the totals are always up to date when a user opens the app. see example attached. app must be able to be added to Goolge play store and apple store