Inclusion Criteria:

• * newly-diagnosed or recurrent glioblastoma undergoing treatment or active surveillance
• * at least 18 years of age at the time of study enrolment
• * Karnofsky Performance Status (KPS) ≥ 70% at time of study enrolment
• * able to comprehend informed consent form and provide informed consent
• * access to patient or caregiver's own Apple iPhone to interface with watch application for documentation of symptoms

Exclusion Criteria:

• * under 18 years of age at the time of study enrolment
• * inability to give informed consent due to aphasia or other language barrier
• * tattoos located on the skin of the wrist or forearm where the Apple Watch will be placed or other skin conditions preventing adequate sensor function
• * inability to tolerate Apple Watch for at least 12 hours per day on at least 50% of days in a four-week period
• * no access to patient or caregiver Apple iPhone to document symptoms