Google announced yesterday Eddystone, an open protocol specification that defines a Bluetooth low energy (BLE) message format for proximity beacon messages.
The specification describes several different frame types that may be used individually or in combinations to create beacons that can be used for a variety of applications.
Eddystone supports multiple frame types for different use cases, and it supports versioning to make introducing new functionality easier. Eddystone is supporting Android, iOS or any platform that supports BLE beacons. Eddystone is available on GitHub under the open-source Apache v2.0 license, for everyone to use and help improve.
Google has also built inside Eddystone a feature called Ephemeral Identifiers (EIDs) which change frequently, and allow only authorized clients to decode them.
Leading beacons vendors such as Bkon, bluvision, estimote, kontakt.io, Radius Networks and Signal360 have already integrated Eddystone.