I have been using HabitKit this year and not really noticed the results. I just tapped when I needed to once a day and can now see the results; a selection of dots and colours that tell a story.
Some of the habits have been blanked out, but they do show that early in the year was not a good time for me and that I was not doing what I should have been doing.
As things improved so did the prevalence of the dots and HabitKit does a very good job of showing the year in a way that will be obvious to almost anyone.
This is not a review, but a small recommendation for an app that does something but in a highly unobtrusive way.