I've always been a fan of audio APIs / mobile SDKs.  For example, if you're watching the Conan O'Brien show and you have the Team Coco app open at the same time, it'll listen to the show and sync up with the show's content, showing the same content or ads on the app as on the TV.  That kind of thing feels like magic to the end user, because there's mystery around how the app is staying sync.

But yesterday, Tim, the founder of ShareThis, showed me something that takes audio APIs to a new level, called Lisnr.  Although it's marketed as a standalone app, my understanding from Tim is that it's also available as an SDK that app publishers can put into its app.

Think of the Lisnr SDK as "Shazam meets a dog whistle."  Tim described it as an audio QR code. The content (whether on a video or a live concert) sends out a sync timestamp audio signal that's outside of our hearing range, but that the microphone on the phone can pick up.  This syncs the phone to the content.

Here's a video of Tim showing this technology off:

At the beginning of the video, the app is "unlocking" content in the app after we listen to an audio track.  Then, after that, the app is syncing its playback to the video on the laptop.  As Tim mentioned to me later, imagine thousands of phones at a concert being held up in the air showing sync'd content on each phone.

Lisnr is a great example of the power of an audio SDK.  I expect that we'll see a lot more innovation in this area -- it's hot.