I love this idea, it can be even bigger than Paypal. Three suggestions:

First, make it a mobile app as a simplified gmail with just the recipient, the amount and a memo. That's it. In version two add the pic, avatar or whatever people use.

Second, open a new wave of email accounts since all gmail accounts are already taken so people can start using their names or businesses as email accounts again. Perhaps GoMail? And start from day one with two factor authentication so squatters don't start their party.

Third, create Merchant accounts and apps so business owners can track thousands of payments a day with tools for money management.

This was my dream solution for the mobile payment need but now that Google is going to do it I'll leave it to them.