One of the cooler new features of both Gmail and Google Wallet that didn't make it into today's three-hour Google I/O keynote is the new ability to send money to any Gmail contact. Just message or reply to someone, write something along the lines of "here's your money, dog," and click the Attachments paperclip icon. You'll see a new option among the expanding icons: a dollar sign. Click the dollar sign, and you can send funds straight from Google Wallet. You can literally attach money to an email. How cool is that?
Of course there are a few restrictions. At the moment you can only send money via Gmail on the desktop, and you need to have either credit in your Wallet account or a linked funding source.