A new smartphone app, developed by researchers at Penn State in the US, graphs caffeine's effect on your body throughout the course of the day, so you'll know if that afternoon cuppa will keep you awake at night.

To plot caffeine's effect with the app, dubbed Caffeine Zone 2, type in information about how much caffeine you drank (coffee, tea, soda, etc.), or plan to drink, and when you plan to have a caffeinated beverage and how fast you plan to drink it.