Google has begun the process or rolling out the new Pay with Google service today. The new way to pay in apps and sites on your phone was teased last May with the introduction of a new Google Payment API. That API would allow developers to add to their apps the ability for you to pay using your Google account.
For consumers, the idea behind Pay with Google and this API is to make purchases frictionless. If you go to a participating app or site, no longer will you have to fill out forms with your name, address and credit card information. Instead, you can tap the Google button and pay for your purchases. The API will feed all of the proper information from your Google account to the merchant to complete your transaction.