Looking at the German version of the Google Play store last week, you may have noticed the "Menthal" app trending at number one and peaking as the seventieth most downloaded app in the country. It also managed to crack number four in the productivity category - one ahead of the Dropbox app.

But, inside the drab cement building at the University of Bonn where the app was created, there wasn't much excitement going on as the smartphone sensation began to rise in popularity. Its chief architect, assistant computer science professor Alexander Markowetz, watched with his team of programmers as the numbers spiked and the servers crashed.

"It's just exploded. So our servers have melted, our infrastructure just wasn't up to the job. And now, several days later, we're slowly recovering."

Soaring popularity

Up to 100,000 people have downloaded the free app so far, the researcher says. Its popularity, in part, comes down to good luck.

Anyone watching the country's most popular reality television program, "Das Dschungelcamp" (Jungle Camp in English) last week would have seen a news teaser for the Menthal app. It was this plug on the late night news bulletin that sent downloads soaring. But while the app is certainly good, Markowetz believes there's something much bigger going on.

You're an addict

Menthal allows you to examine your own phone behavior and see just how much time you are using your smartphone.

"Our promise would be that if you want to go on a digital diet, we provide the scales. So we measure what you do and how often you flick on your phone," adds Markowetz.

While smartphone addiction is self-evident today, the idea didn't exist a few years ago.

"We called it funny behavior - we didn't have a better name for it. Constantly checking Facebook, checking news, checking WhatsApp, playing online games," the computer science professor says.

At the end of the day, Markowetz says, your smartphone is like a slot machine. One little action - activating your phone - is like pulling the handle. Will I get an email this time? A news story? And will it be a good email, or a good news story? Once in a while there's a good one - a reward of sorts - which only keeps us coming back for more, he warns.

Shocking results

When the first round of data came in from a six-week pilot study of 50 students at the University of Bonn, the results shocked the project's co-researcher, psychologist Christian Montag.

"The two aspects were really surprising. The one aspect: people activate their phones 80 times per day, which means you're either online or thinking about getting online again. The next surprising fact was that the classic features of a smartphone - namely telephoning and sending texts - make up only a very small part of today's phone use."

Fifteen percent of users' smartphone time was lost to WhatsApp. Thirteen percent went to gaming - another nine to Facebook. The researchers study showed that male subjects tended to be the gamers, while females spent more of their time on social networks.

Time waster

At a popular coffee shop in Bonn, just like any other across the Western world, it is easy to see what Montag is talking about. Two women in their early twenties ostensibly talk to one another, while simultaneously checking and typing away on their smartphones.

When asked why they sit in a café with smartphones in front of them, Julia says she likes to show her friend Lisa messages or photos she's received. Then, "we talk about the message," she adds.

But, what was more alarming, while the two young women were 'talking' with one another, they both admit to communicating with other people outside the café.

That would account for the fact both say they spend more than five hours a day actively using their smartphones.

But, that's above average. According to the Bonn researchers, 25 percent of the participants spent two hours or more per day on their phones.

At Bonn's central train station, Frank, a German priest, is in the lower range. He says he's only stuck to his phone for 30 to 40 minutes each day. Some of this time, he adds, is spent reading his digital bible. Still, he thinks an app like Menthal could help him wean that figure down.

"I think that's a pretty good idea. Because I'm realizing that my smartphone really eats my time. I'm really pissed off with that."

Regardless of the extent of smartphone addiction, psychologist Montag has a concrete piece of advice: wear a watch.

"[Smartphone users] have to look at the clock because they often don't wear a watch anymore. And then they say, I could probably do something else. So for all the people who think they have problems, start wearing watches again, because this will cut your smartphone behavior in half."

For now, Menthal is only available for Android phones. Markowetz and his programmers are trying to get the app's functions to work within the more restrictive architecture of Apple's iOS operating system.