Have an iPhone 4? Want some of that hawt NFC action? If your bank provides smaller credit cards with NFC chips, you can add one to your iPhone 4 right now. All you have to do is remove the back cover of your iPhone 4, position the card behind the battery and you're all systems go. The glass backer is said to be thin enough for credit card terminals and the source says that they've had success scanning it with thick cases.
So if you'd like to get your NFC on (why is it when I type NFC, I automatically type KFC and have to re-type it... nicely played, NFC) then do so at your own peril. If you do the NFC upgrade, please let me know how you went!