This document discusses augmented reality on Android devices. It provides an overview of the DroidAR framework, an open source library for building location-based and marker-based augmented reality apps on Android. The document outlines features of DroidAR versions 1 and 2, such as using the jMonkey game engine and sensor-based tracking. Examples of indoor navigation and surface detection extensions are also presented. The conclusion emphasizes DroidAR's flexibility, ease of use, and suitability for scenarios like games, navigation apps, and multi-user experiences.