Background: Heart disease is a leading cause of death. People can reduce their heart disease risk by exercising more. Mobile health technology may make people more successful at increasing their exercise. This includes things like physical activity monitors and smartphone apps.

Objective: To find out if mobile health technology can increase physical activity.

Eligibility: African American women ages 21-75 who: * Are overweight or obese * Live in certain areas near Washington, DC * Have a smartphone that can use the study app

Design: At visit 1, participants will * Answer survey questions. These may be about medical history, physical activity, and weight. They may also cover body image, health perception, and spirituality. * Have body size measured and get blood tests * Get a device to wear on the wrist. It will record physical activity and hours of sleep. * Learn how to download and use the study mobile app For 2 weeks, researchers will collect data about participants physical activity. Then participants will have a study visit with additional blood tests. All participants will get messages from the app that encourage exercise. Some participants will get data from the app about exercise near their home or work. Some participants may get face-to-face coaching. Participants may get wireless devices. These measure body weight, blood pressure, and blood glucose. Participants can measure these at home and upload the data to the app for the study. Participants will have visits after 3 and 6 months. They will repeat the visit 1 tests.