Google has introduced Nearby, a new way for smartphone users to discover and communicate with each other. Nearby will utilize Bluetooth, Wi-Fi, and an inaudible sound to establish proximity for the communication. With this new API, people will be able to communicate cross platform between Android and iOS. With the most recent release of Google Play Services 7.8, all developers can have access to the new API, and the best part is Nearby does not require a Google Account.
Google has already built the technology into a couple of its own services, like Chromecast Guest Mode, Nearby Players in Google Play Games, and Google Tone. A few third-party developers have already implemented it as well. In Trello you can easily share a board with those around you, or in Pocket Casts you can find and compare podcasts with others around you.
Source: Google Developers