Caffeine consumers often walk a fine line between alertness and jittery nerves. A new smartphone app developed by Penn State scientists promises to help them keep track of their intake for the perfect caffeine buzz.

For many people, caffeine intake is the only way they can get going in the morning. Geula Buchnik who owns a cafe in Philadelphia's Old City said she doesn't talk, think, or do anything before she has two cups of coffee in the morning.

How to keep going without overdoing it is something many people struggle with, said Penn State scientist Frank Ritter, who developed the "Caffeine Zone" app. More does not equal better when it comes to alertness, said Ritter.

"It doesn't help to have two or three times as much. It doesn't make you two or three times as alert, because it gets you out of the optimal zone," he said.

According to Ritter, the optimal zone for a perfect caffeine buzz is between 200 and 400 milligrams of caffeine in the blood stream depending on a person's weight and caffeine habits.

Ritter says the app, available in free and paid versions, allows people to track how much caffeine is currently in their system, and calculate how quickly the caffeine is being processed.

Ritter says drinking too much caffeine can make people shaky and nauseous, as well as affecting fine-motor skills. It can also have an impact on mood -- something that latte macchiato fan Kevin Greer knows firsthand.

"I can be really happy and fun, and then something will happen and I will get very frustrated," Greer said.

Ritter said the app allows people to time consumption to allow them to rest, to make sure that caffeine levels will have dropped enough for them to sleep. Ritter says the app could be helpful for people who do shift work and have constantly changing schedules.