This is a smart way to integrate with Pinterest while they work on a proper API — it’s similar to how some apps passed photos to Instagram before they had a proper mobile write API (which is still limited to Hipstamatic, I believe).
Here’s a quick video showing how it works.
I get the feeling that Pinterest write API access for mobile will be huge. Huge as in, a lot of startups are going to integrate it before they worry about something like Google+. It will be Facebook, Twitter, Pinterest.