[mseebach]

I've thought about a similar idea, except in mine, you send a "locked" payment via email to the recipient, and give him a pin-code to unlock the payment. This allows for exchange of money in person (say, you're buying a used car from someone, and want to see and drive it before handing over the money, and don't want to carry the cash - neither party trusts each other to wire the money ahead of time or after).

The recipient can easily verify and claim the transfer using phone, SMS or online.