It's a phone, it's a web browser, it's a ...
Gone are the days when phones were just for talking to people on. Anything you could possibly need, "there's an App for that". You can make music, movies, and connect with the world with the touch of the screen.
In a K- 12 school, smartphones can be used in middle and high school classes to record teaching or lectures for students to use as reference material. There are also programs such as the one available at www.polleverywhere.com which allows students to use their phones to give their answers to questions and for teachers to see these answers. There are more programs being developed to incorporate this type of tech into the classroom.