In the filing, Amazon says that many people do not like giving up personal information online, as that makes them feel vulnerable when it comes to identity theft. Amazon's system would use temporary tokens that could be exchanged once the sender requests that a payment be made, or the recipient requests the funds. For example, you could make a payment of $20 by sending a text message to Amazon that reads "PAY 20," which would be quickly followed by a return message with a code tied to the account of the sender. If the code is sent to Amazon by the recipient, his account would be credited the $20. In the patent, Amazon suggests that the code could contain part of the recipient's phone number. It wouldn't be enough of the number to identify the person, but be unique enough to make sure that no one else could send the code back to Amazon.
Other ideas mentioned by Amazon include putting an expiration date on the code for a single redemption, or allowing the code to remain open for multiple payments over a set period of time. And while Amazon isn't a financial company like American Express, or used to wiring funds like Western Union, it does have a world-wide presence thanks to its online store. If Amazon does go ahead and implement this plan, it would be competing with PayPal, owned by eBay.
source: USPTO via Slashgear