In the past, if you wanted to add NFC (Near Field Communications) to your iPhone, it involved getting down and dirty and doing some soldering. The newest hack however provides an invisible solution, granted you are comfortable removing the back of your iPhone 4.
To give some more information about NFC, it allows users to just tap their phone to a new credit card terminal and the phone makes the payment for you. The process here involves ordering an NFC card from your Bank, or Credit Card Company. Then, simply remove the back of your iPhone and attach the new NFC card to your iPhone’s battery. You can see the card on the above image, on top of the battery. Then just reattach the back glass and you’re all set.
Now this hack obviously only allows you to use one credit card NFC and not use multiple like a normal NFC chip in another device would give you. But if you really want near field for your Debit Card, then this may be the way to go for you. The one thing I would be worried about is the heat that the battery gives off. The phone was designed to dissipate that heat properly, but putting a plastic card on top of that may distort that. But if you’re brave, no reason to not give it a try, if all else fails, you can always remove the card the same way you put it in the phone.