Send money to anyone for free from a linked bank account; with small fees via credit cards
It wasn't a headline part of the Google I/O 2013 keynote, but the Google Commerce Blog has just dropped a pretty sweet feature on us -- the ability to send money to anyone from Gmail with Google Wallet. The option is being rolled into Gmail as just another thing that you can attach when sending a message. Right next to the paperclip for attaching files you'll see a "$" icon where you can click and send money free of charge to the recipient -- who doesn't have to have a Gmail account -- if you have a bank account connected to your Google Wallet account. Transfers sent by an attached credit or debit card are assessed a small transaction fee, and it is clearly shown when sending whether or not there will be a fee.
The ability to send money via Gmail will roll out over the coming months to U.S. residents over the age of 18, and won't be available on mobile through the Gmail app but will be possible with the Google Wallet mobile website. We would expect that once the security aspect of sending money on mobile gets figured out that the feature will hit the Gmail for Android app eventually.
Source: Google Commerce Blog