The Caffeine Zone app was developed for iOS by two doctors at Penn State University. Possibly unsatisfied with gauging their caffeine levels intuitively, Frank E. Ritter and Kuo-Chuan Yeh decided to hit their habit with some science. After delving through some peer-reviewed studies on the drug, they determined that the optimal caffeine level for mental alertness and feeling generally awesome falls between 200 and 400 milligrams. While everyone metabolizes the stuff a little bit differently, the way it acts upon the body and brain is pretty well understood. Drink a cup of coffee and you'll hit prime caffeinated status within about an hour. Your body will then work to get rid of it at a rate of one half-life every five hours.
With the app, you'll be able to visualize your own caffeine levels with handy, science-y charts and graphs. Simply tell your phone when you consume a caffeinated beverage and what kind, then track your buzz's progress throughout the day. It'll tell you how much you need to drink to stay in the optimal alertness zone and it'll also warn you when you're about to drink so much that it'll interfere with your sleep schedule. So if you find your habit has been keeping you up after hours, check your intake against the Caffeine Zone app to make sure you're not overstimulating yourself too late in the day.
The scientists behind the app recommend that caffeine users start their days with one large dose, like a big hot latte, then taper off their drinking rates as the day goes on. If you're a strict coffee drinker, you might want to consider brewing weaker and weaker cups as the hours tick away. Tea-friendly users could go from coffee (or yerba mate) to black to green, a pattern I actually picked up on intuitively before I'd even heard of the Caffeine Zone. It makes for a nice slow burn all day, plus you get all the health benefits of all three drinks. Those who are strict energy drink users should probably just consume less of their poison of choice anyway.