Lack of physical activity is associated with negative health outcomes, including obesity, diabetes, and cardiovascular disease. There are calls from NIH and medical organizations to integrate the use mobile devices, such as smartphones, to provide "e-health" interventions to patients in their daily life. Referred to as Ecological Momentary Interventions [EMI], these innovative mobile methods provide an opportunity for researchers and clinicians to offer tailored intervention material to people at specific times and in specific settings when they may be most in need of such support. To our knowledge no study has used objective ambulatory assessment data to deliver EMI. This preliminary work is to demonstrate the feasibility, and test preliminary efficacy, of using a Bluetooth accelerometer to provide real-time feedback on a smartphone to increase objectively measured steps (i.e., increase activity). A within-person design will be used, including assessment, intervention, and follow-up phases. During the assessment phase objective physical activity (using accelerometers) will be collected. In the intervention phase participants will also receive real-time feedback throughout the day regarding their total steps and personalized step goals. Objectively measured steps and disease status measures will be used to evaluate efficacy.