PREAMBLE: this question is wildly obsolete. There's no more Google Checkout and no more API.
Android Market uses Google Checkout for paid app sales. Google Checkout has a fairly extensive API. The behavior of Android Market accounts is markedly different from that documented for vanilla Google Checkout. Some examples:
- URL callbacks upon sales don't work
- Some XML API methods are not supported - e. g.
<archive-order> - In XML notifications, undocumented elements - e. g.
<agent-private-data>under<shopping-cart>
Are those Android specifics documented anywhere?