Estimate the amount of caffeine in your system at a given time.
Example:
7:00 am - drank 200mg,
12:00 pm - still 100 mg left,
5:00 pm - 50mg left + drank a soda so,+60 mg. 10:00 pm bedtime, 75 mg remaining.
More data relating to how caffeine might be affecting my sleep, workouts, etc.