This document discusses the mobile platform market and levels of openness. It describes the history of mobile platforms from 1G to 4G networks and the evolution of devices from basic phones to smartphones. The major mobile platforms are described - Symbian, BlackBerry, iOS, Windows Mobile/Windows Phone 7, and Android. Factors for developers to consider when choosing a platform are discussed, such as the application purpose, target audience, and platform limitations. Levels of openness for platforms are also covered, with Android and Symbian noted as the most significant open source options.