What technology are they using in this Shopkick demo to achieve pinpoint geoLocation?

I know they have some hardware installed around the store but what does the hardware do and how is it interpreted by the app?

(at one point they show hardware attached to the celling in one of the locations they are in)

WOAH sorry forgot the link, http://techcrunch.com/2010/08/03/shopkick/

Thanks!

In the video, they refer to the beacon emitting sound that the device detects.