The Proximity Platform SDK enables peer-to-peer communication between mobile devices and computers over Bluetooth without an internet connection. It allows applications to discover and communicate with each other nearby without requiring WiFi network configuration. The SDK provides messaging, low power operation, cross-platform compatibility across Android, iOS, OSX and Windows, and various proximity detection features. Developers can get started by creating an account, registering an app, and using a provided key and sample code for each platform.