Smartphones are in the process of replacing cameras, phonebooks, land lines and maps ... and wallets are next. First announced in May but just launched today, the Google Wallet free app allows its users to store electronic versions of their credit cards on their smartphone, and pay for items simply by tapping their phone on a near field communication (NFC) reader at a store's front counter.

A number of retailers, along with one financial institution and one carrier are on board, and so far Google Wallet is compatible with the Citi Master Card along with Google Prepaid Cards, that can be "loaded" using any existing credit card. Currently it only works with Google's Nexus S 4G phone, on the Sprint network. Needless to say, the number of cards, devices and networks is expected to grow soon.

It can be put to use at merchants that display a MasterCard PayPass symbol at their till. Users simply enter their PIN on their phone, tap the device on the merchant's NFC reader, and the payment is electronically made. At some retailers, electronic coupons and loyalty points will also be passed along. Participating businesses can be found using the MasterCard PayPass Locator for Android app.

Special Google Offers will also be made available to users, and will automatically sync with their Wallet.

Down the road, Google would also like to see the Wallet containing things such as gift cards, tickets, boarding passes, and even electronic house keys. Google Wallet can be downloaded now, free of charge.

Other companies that have experimented with similar payment technology have included Orange, SIMlink, SAGEM, and Visa.