lines of C , 2.1 million lines of Java, and 1.75 million lines of C++.[18]" from http://en.wikipedia.org/wiki/Android_%28operating_system%29#Software_development It also says the officially supported IDE is Eclipse . Many android devices have built in sensors. See http://www.vogella.de/articles/AndroidSensor/article.html (added March 29, 2011) Also see http://www.vogella.de/articles/Android/article.html -- "This tutorial describes how to create Android