My students are using iDiary for the first time this year. It is a very simple journal app. On shared iPads each student can create their own password protected diary, complete with color preferences and a mascot. I rotate this app so each student has a chance to create a free-response entry 1-3 times a week. I don't read these entries.
In addition, I occasionally assign a specific topic to a diary entry. This week after seeing the play "Harry the Dirty Dog" I asked students to comment on what they liked and didn't like about the performance. They took a screenshot and emailed it.
In the diary entry students have the ability to add stickers, draw, import a photo, write with a pencil and type. It gives them plenty of ways to express themselves.