Is there an API from Square that allows me to accept payments within my mobile application?

[George]

Hi @btnz, good timing! We just announced our Build with Square Payments APIs (E-commerce API and Register API).

With our Register API, you can build your own app for powering in-store or mobile payments.

Take a look at http://square.com/developers and our blog post introducing the initiative: http://squ.re/1RQAF2T.