Datalove (free) is a simple iPhone app that offers you many ways to record, display, and explore your data so that you can asses trends in your current daily habits.
How many hours do you study per week? How much weight are you losing or gaining every month? How long and how far do you run? Looking at this data will help you set manageable goals and see which areas you could improve on. You can even define custom activities to fit your lifestyle. You could, for example, record the number of minutes you spend on the phone with your family and friends every day.