Note-taking app for audio; $9.99 for iPhone, iPod touch and iPad
If you've ever listened to a song and been hit with a burst of choreographic inspiration, you know the frustration of not being able to quickly commit that choreography to paper. Notetracks is an app that allows you to embed notes within a song's audio waveform, so you can document exactly where and when you want a specific step or formation to happen. It's easy to use: After importing songs from your iTunes library or Dropbox, you can assign markers to specific moments within a track and then write or record notes for what should happen at each marker. Add text or symbols or even draw your ideas and comments.
With the app, you can share whatever project you're working on with other teachers, either as a PDF of the audio map or with permissions to review, modify and collaborate on it.