Blippy and Swipely both launched fairly recently with the hopes of making spending a social experience. Both services are very similar in that they both allow you to connect your bank and credit card info, as well as other accounts like iTunes and Amazon. After you've set everything up, as you start spending, you have the option to share these purchases with everyone. And now you can extend that sharing with the Blippy API.
Buyvite Group Pay, a social payment platform allowing multiple people to contribute to a single payment transaction, has announced the launch of the Private Label Group Payment API which allows social payment and cost splitting functionality to be added to e-commerce websites and applications.