Inclusion Criteria:  Patients of Pediatric Cardiology at the Stollery Children's Hospital in Edmonton, AB Group 1: infants <12 months of age with single ventricle physiology or biventricular cyanotic congenital heart disease Group 2: patients aged 5 to 17 years with heart failure, listed for heart transplant, or within 1-year of heart transplant English speaking Access to internet either in the household or within the community  Exclusion Criteria:  Inability to use technology due to physical or cognitive impairment in the caregiver Non-English speaking (thus limiting communication during qualitative interviews) No access to the internet (thus unable to transmit the device data through the app or be able to complete the qualitative interview)