A Study to See if an iPhone Weight Management App Can Help Promote Weight Loss in Adolescents and Young Adults After a Stem Cell Transplant

Inclusion Criteria: * Patients with a history of HSCT of any type, at least 100 days post-transplant at initial consultation of the study, will be eligible for the study * Patients must classify as obese, represented as body mass index (BMI) \>= 85th percentile for age and gender * Patients must also be able to read English since the app intervention is only available in English form * No patients will be excluded for any specific underlying medical condition, but decisions will be made on a case by case basis if a patient's functioning is deemed to significantly interfere with intervention participation * PARENT: * His/her child meets all inclusion criteria * \>= 18 years of age * Can speak English Exclusion Criteria: * Patients who are \< 100 days post-transplant at initial consultation will not be eligible for the study, but may become eligible if they are \> 100 days post-transplant at their next consultation that falls within the enrollment window * Patients whose BMI does not fall under the obese category will be excluded