Here is an interesting piece from SwitchEasy designed specifically for the iPhone 4 & 4S with this card holding mechanism providing easy storage for single smartcard or debit card. Supports direct debit on all contact based smartcards and debit cards and is made from scratch-resistant polycarbonate and sandblast finish design for best grip experience. Completing the design is an auto lock function and slide button for easy ejection of the smartcards and debit cards.