Facebook is adding a fitness tracking app to the company's store of acquired companies. 

Moves, a self-desribed "all-day activity diary for smartphones", announced yesterday that Facebook had agreed to acquire the company and app. 

Financial details of the deal were not disclosed. 

In an announcement on Moves' website, the company said it would be working with Facebook on "building and improving their products and services with a shared mission of supporting simple, efficient tools for more than a billion people,." 

For the time being, Moves will continue to operate as a standalone app, and the company said it has no plans to change that or "commingle data" with Facebook.

The buy comes as Facebook continues to strengthen its position as a mobile company. On Wednesday, Facebook report first quarter earnings that counted 1 billion active mobile users. Meanwhile, mobile accounted for 59 percent of Facebook's ad sales.