The Isis Mobile Wallet is a free app at the Google Play Store. The mobile payment service is a partnership between AT&T, T-Mobile and Verizon. For your Android phone to support Isis, it must have NFC and a special SIM card that keeps your personal payment information secure. And you need to have credit card account information from a participating issuer loaded into the virtual wallet so that you can tap and pay at stores that accept Isis.
If you own an Apple iPhone, you can uses Isis thanks to the special Isis ready cases available, that are embedded with NFC connectivity.
source: Isis (Verizon|T-Mobile|AT&T) via Phonescoop