Inclusion Criteria for HCT candidates:  Children, adolescents and young adults (AYA) 6-26 years of age who are HCT candidates  Recipients within 30 days prior to or within 14 days after autologous and allogeneic HCT.  -. Any preparative regimen.  Willing and eligible to enroll on PA19-0756  Inclusion Criteria for Healthy Donors:  - Healthy HCT donors between the ages of 6-26 years of age.  Exclusion Criteria:  Any subject who does not consent/assent to participation.  -. Any subject with an injury or deformation to the index finger which prevents proper fit of the device.  Any subject with skin toxicity or neuropathy which prevents comfortable use of the device.