The Mobile Sensor Actuator Gateway (MSAG) by Ericsson Labs provides an easy-to-use API for accessing on-board mobile phone sensors in standardized formats, facilitating rapid prototyping of sensor applications. It allows developers to retrieve sensor descriptions and data, supporting various sensors like temperature and accelerometer, while also geotagging and timestamping the data. The SDK is compatible with Android devices version 1.5 and later, and includes examples for implementing the API in mobile applications.