Inclusion Criteria:  Patients age 15-39 at the time of study entry Patients must be within 3 weeks of starting anti-cancer therapy  Patients must have a diagnosis of Hodgkin lymphoma, non-Hodgkin lymphoma, sarcoma and have plans to receive anthracyclines or radiation therapy to the chest OR  have a diagnosis of a central nervous system (CNS) tumor OR have plans to receive a stem cell transplant Patients must have smartphone device and regular access to internet Patients must be English-speaking  Exclusion Criteria:  Patients that are a ward of the state