IBeacon

*iBeacon is a protocol standardised by Apple Computer and introduced at the Apple Worldwide Developers Conference in 2013.[1] Various vendors have since made iBeacon-compatible hardware transmitters - typically called beacons- a class of Blue Tooth low energy devices that broadcast their location to nearby portable electronic devices. The technology enables smartphones, tablets and other devices to perform actions when in close proximity to an iBeacon.[2][3]

iBeacon uses Blue Tooth low energy proximity sensing to transmit a universally unique identifier[4] picked up by a compatible app or operating system. The identifier can be used to determine the device's physical location[5] or trigger a location-based action on the device such as a check-in on social media or a push notification.* http://en.wikipedia.org/wiki/IBeacon

Google Eddy Stone is Cross Platform and Open Source.