http://satpredictor2.deere.com/ predicts the visibility of GPS or GLONASS satellites for a given position elevation and time.
Shopkick uses the build in microphone of a smartphone, currently iOS or Android based, to triangulate its position via a network of ultrasonic beacons. Other then satellite based systems like GPS this allows a more precise location tracking especially in indoor situations where GPS is not or poorly available. Shopkick did a first installation in a Best Buy in San Francisco as part of a POS application.
See also this article here: technologie review article …
Researchers at Fraunhofer institute developed a compact tracking system made to be installed in Gameconsoles.