With Moodio you can easily log your mood with just a couple of taps without writing a word. Features: Powerful statistics, daily and monthly breakdown of your moods, Dropbox sync.
Interesting idea, curious how this would effect the persons moods after using it if they see they were very sad or very happy the week before. Research idea ;) Are there reminders sent throughout the day or something to remind the person to log?
AnyLingo