PayPal has unveiled a peer-to-peer payment functionality that allows Android users to pay each other by tapping two NFC-enabled devices together, report Telecompaper. The system leverages a PayPal widget that allows users to request or send money.  The service will initially be available this summer in the US with the Samsung Nexus S from Sprint and T-Mobile, but the company plans to expand it to other Android phones that include NFC functionality in the future.