Racecar theme with students from one class "competing" against another in the hallway. One suggestion -- to follow AR best practice, make the "pit stops" 10%, 20%, 30% (etc.) progress toward their goal instead of 5, 10, 15 (etc.) point levels.
I believe that this a wonderful bulletin board idea for my future classroom. This would be great to coincide with March Madness. This would be especially interesting for sports fans who are a little reluctant in math class.