That's an android app API. See andrenotgiant's comment (sibling to yours) that links to a REST API. What I have in mind is letting people export photos into a folder to populate a photojournal, as I'm already doing with Dropbox.

[EDIT] Looking deeper I see they're the same API. [/EDIT]

It's a good thing I read HN. From the Google announcement alone I would not be aware of either API.