I usually use a credit card while purchasing something. The main disadvantage of using credits cards is that it is difficult to monitor spent money.
I want to have a wallet which will inform me about all changes with my bank account and will adjust to the sum of money available:
* It will vibrate / beep each time a transaction take place;
* When there isn't much money in bank account the wallet will resist its opening;
* It will swell and shrink to reflect the balance in bank accounts.
The wallet will work by communicating with the owner's mobile device via Bluetooth, using its data to pull financial information from bank accounts.
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