OpenCab is a set of interface definitions that permit multiple mobile apps running on a single device to communicate with each other at runtime to present a seamless experience for the driver. It's designed to serve truck drivers and other field users who drive vehicles as a key part of their jobs.

Although this documentation is in the form of a Java API, OpenCab isn't an SDK. Instead, it's a set of agreed-upon Android Intents and ContentProviders that, if implemented according to the definitions documented here, permit cross-app communication of structured data without a proprietary SDK.

Check out org.opencabstandard.provider for the technical details about the types of data that can be shared between apps.

Packages 
Package Description
org.opencabstandard.provider
This package contains the Java interface files that define the contracts for OpenCab providers, the data types communicated to and from those providers, as well as abstract implementations that reduce the boilerplate code needed for an implementation.