Typatone comes from the makers of Patatap. In the latter, you are basically able to create visual fireworks by typing on a keyboard, as each key corresponds to a shape and sound. Typatone is similar, but it allows you to create music with a sentence.
The website is free to use. There is an app available for .99, but I think free works pretty well for me;)
How can you use this in class? We discuss synesthesia in my 4th grade GT class, so Typatone can definitely augment that discussion. Also, I think the students would enjoy writing poetry or sentences with figurative language to see how they sound. How about a spelling test? Allow students to listen to the sounds of different letters, and then have them guess what word you just spelled. Music teachers can probably think of a few applications also.
Creations can be shared through e-mail or embedding (although the embedding option apparently does not work in this blog). You can click here to listen to the short tune I composed.