Inclusion Criteria:  Have been diagnosed with breast or prostate cancer and treated with cardiotoxic therapy (e.g. anthracyclines, chest radiation, trastuzumab, aromatase inhibitors, or ADT) Have ≥2 cardiovascular risk factors (e.g. hypertension, diabetes, dyslipidemia, obesity) or known coronary artery disease (prior coronary revascularization, myocardial infarction, or coronary stenosis > 70%) Self-identify as Black or Hispanic Are at least 2 years from their cancer diagnosis and have no evidence of active malignancy or acute illness that would limit study participation Own a smartphone or tablet compatible with the wearable device Are able to read English or Spanish Are able to provide informed consent  Exclusion Criteria:  Currently participating in another physical activity research study Have any medical conditions prohibiting ambulation without assistance Any other reason why it is not feasible or safe to complete the entire 9-month study Step count > 7500/day during the baseline data collection period