BOSTON -- Mobile devices have tackled an ever-expanding list of functions in recent years, but one new application for the iPhone is promising users a unique service. It's supposed to make you happier.

Developers at Happier.com launched a companion application for the Apple iPhone and iTouch this week that allows users to keep track of how happy they are from day to day using a mobile “gratitude journal.”

The software, which developers said is based on scientific research on happiness, requires users to log three events each day that made them feel happy, and fill out a 24-question survey gauging their emotional state.

“It’s so easy to focus on what goes wrong in our lives, but studies show when you focus on what’s going right you live a happier, more fulfilling life,” said Andrew J. Rosenthal, vice president at Happier.com.

Rosenthal said that the application analyzes patterns in individual users records and provides feedback on which circumstances are most likely to produce positive emotions.

The company launched a Web site in November which has 10,000 registered users, according to Rosenthal.

The site is currently free to use and offers a variety of tools similar to the gratitude journal that help users to understand which events in their lives generate the greatest meaning and positive engagement, according to the company.

In addition to logging daily entries in the iPhone journal, users are asked to regularly fill out a survey that measures several happiness metrics.

Questions ask users to pick between choices like “I feel like a failure,” “I don’t feel like a winner,” and “I feel like I have succeeded more than most people,” and the software uses the answers to generate a happiness score.

This number provides a basis for users to chart their progress and change in day-to-day fulfillment, according to the company.

“Unlike a diet where you give up an ice cream soda, these tools are addictive,” said Rosenthal. “They make you feel good.”

Developers at Happier.com also benefit from the tools they construct, according to Rosenthal, who said that the site has been helpful in managing the stresses of a first-year business.

“Colleagues and I use this every day,” he said. “We’re a start-up company, and things are tough for a small company right now. We use these tools to help stay focused and balanced, and we know that our users do.”