*Image courtesy: © Thinkstock photos/ Getty Images

*Text courtesy Reuters Health

(Reuters) - Trying to get fit or lose weight but lacking the motivation and willpower? A new app that acts like a digital personal coach monitors fitness, activity, sleep and diet and provides tips for health and productivity.

The app called Larklife gathers data via a wristband and provides personalized advice which is displayed on the smartphone app. It can deduct if the wearer is not getting enough sleep and how sedentary they are, according to its creators.

"In the background it's as if you had your own personal fitness trainer, productivity coach and sleep coach all working together to give you the easiest way to improve at this moment," said Julia Hu, CEO and co-founder of the Mountain View, California-based company Lark.

After a poor night's sleep, for example, the app might suggest extra protein for breakfast, based on research that it can improve mental focus when someone is sleep deprived. Thirty minutes after a workout, it might remind the user to drink water to keep hydrated.

The app is part of the growing wearable technology market, which is expected to nearly double by 2014, according to a report by research firm Juniper Research. Many wearable technology devices connect with smartphone apps to display the data they gather.

There is a growing supply of health and fitness tracking apps and gadgets on the market, including the Nike+ FuelBand, Fitbit and Jawbone UP, but Hu said her product provides real-time advice and does not focus on tracking metrics like calories burned or distance traveled.

"Data is incredibly important as the first step, but the layer on top that everyone is missing is ‘what does this actually mean for me?" she said.

Most people don't care about shaving 10 seconds off their running time, she added, but they do want to lose a few pounds, improve productivity and have more energy.

The Larklife app provides its coaching wirelessly in real-time.

"When we're building good habits it's important to have that positive reinforcement in real-time," Hu explained.

All the advice that the app provides is based on real-time data from the wristband, such as a reminder that the wearer has been sitting for more than 100 minutes and should walk around.

"It's a gentle nudge and friendly reminder at the time when you're supposed to be doing it that just pushes you to take that extra little step," explained Hu.

The company said it developed the app with sleep, nutrition, fitness and circadian rhythm experts and neuroscientists.

For dieters the app automatically logs meal times and can record more detailed information, such as type of food consumed. It will be available for iPhone and iPod touch devices in December. The wristband will be sold in Apple stores and online in the United States in December for $149.99.

(Editing by Patricia Reaney)