Instructors can reach the largest number of student phones by creating messages using HTML5.  There are compelling reasons to begin using HTML5 as soon as you can. Instructors will be able to move to multimedia messages using either Audio and/or Video short messages, and reach the largest number of student phones. Don't forget students with a top of the line iPhone or Android phones will receive, and render your messages no problem. To reach all the students you need to create messages that render on the less-than-the-best cheaper phones.