Inclusion Criteria:  Able to read and speak English; Has a smartphone; Lives in the Philadelphia area; Age 14 or older; Able to provide informed consent; Enrolled as a member of a 2 to 5 member family team with least one member 65 years or older.  Exclusion Criteria:  Already participating in another physical activity study; An 18-month physical activity program is infeasible (e.g., metastatic cancer, unable to ambulate or provide informed consent) or unsafe (currently pregnant or told by a physician not to exercise); Do not have sufficient eyesight or dexterity to operate device; Average step count greater than 7,500 steps/day during the run-in period.