Eddystone (Google)

Eddystone is a Bluetooth Low Energy beacon profile released by Google in July 2015. The Apache 2.0-licensed, cross-platform, and versioned profile contains several frame types, including "Eddystone-UID", "Eddystone-URL", and "Eddystone-TLM". "Eddystone-URL" is used by the Physical Web project, whereas "Eddystone-UID" is typically used by native apps on a user's device, including Google's first party apps such as Google Maps.
Background.
The format was named after the Eddystone Lighthouse in the UK, motivated by the simplicity of a lighthouse-signal and its one-directional nature.
Technical details.
Though similar to the iBeacon profile released by Apple in 2013, Eddystone can be implemented without restriction. Eddystone also contains a telemetry frame ("Eddystone-TLM") designed for reporting on a beacon's health, including, for example, battery level. Like other beacon technology, beacons with Eddystone can give devices a better indication of what objects and places are around them. Importantly, beacons do not generally accept connections from other devices, meaning that the beacon itself cannot record what devices are in its vicinity. In many cases, the simplicity of the beacon frame means that an app (for example Google Chrome) is required in order to interpret the beacon's signal.
Nearby Messages is the API that can be used off of this protocol to receive data that is stored within beacons. Differing from iBeacon, Google beacons use not only Bluetooth but also WiFi and near ultrasonic sounds to communicate between devices.
Eddystone has 4 frame types.
Google beacon platform.
In tandem with the Eddystone, Google launched the Google beacon platform. The platform includes the Proximity Beacon API designed to associate content with individual beacons. The Proximity Beacon API fronts a registry of beacons where extra information (known as "attachments"), useful to developers' applications, can be associated with individual beacon IDs. Several attachments can be associated with a single beacon. Attachments can be updated in real-time and can be retrieved by an app using the Nearby API in Android (through Google Play Services) and the Nearby library for iOS.
Waze Beacons.
The navigation platform Waze have deployed their brand of Eddystone beacons in tunnels around the world (where GPS would not work)
They transmit the following data
They will ignore this information from any beacons that do not use an ID number belonging to Waze
Security.
In 2018 the security of the platform came under scrutiny from privacy advocates with concerns over how the audio component of the beacon is recorded, stored and ultimately filtered to just the ultrasonic portion of the signal. Without proper informed consent, users may find their conversations are illegally being recorded by beacons using the Eddystone protocol in collaboration with the Nearby Messages API.
Discontinued date.
On December 2018 Google stopped delivering both Eddystone and Physical Web beacon notifications. 
The low number of users and the poor user experience were the reasons to discontinued the Eddystone beacons announced by Google. It still continue to have access to the beacon dashboard and can deliver proximity based experiences similar to Nearby Notifications via your own apps using our Proximity Beacons API.