Price: free but with in-app purchases, $4.99 for the full .edu app with everything
Describe local history or architecture
Describe a drawing or artwork
Have your character tell a story about an image
Introduce a person in history
Explain a diagram or a cell
Recite a poem or part of a speech
Describe a time in history
Speak in a foreign language
Include them as a part of a larger video
Introduce a lesson or give homework instructions
These are just a few ideas. I'm sure you can come up with even more.
On the plus side it's very easy to use and allows the students to create a character and record their voice speaking over any image available on the iPad. It's fun and a great way to present information in a new and creative way.