Inclusion Criteria:  Patients planned for one of the selected surgery types: Cardiopulmonary bypass (CPB) surgery (Maastricht UMC+) Coronary artery bypass surgery (Maastricht UMC+) Cardiac valve replacement (SAS, Maastricht UMC+) Prostate, kidney, and bladder cancer surgery (INRCA) Hip and knee replacement (HSJD; Parc Tauli) Maxillofacial surgery (HSJD) Orthognathic surgery (HSJD) Scoliosis (HSJD) Signed informed consent (by patient or legal guardian in paediatric cases). Patients ≥ 18 years old, except for paediatric Hospital San Joan de Deu (HSJD) ≥ 8 years old. Patient owns a smartphone with Android version 4.4 or above. Patient (or legal guardian/caregiver in paediatric cases) is able to demonstrate basic digital literacy (e.g. knows how to communicate through instant messaging apps or similar).  Exclusion Criteria:  Dementia. Pregnant women. Inability to understand the local language. Allergic to dedicated wearable material (stainless steel and silicone). Currently enrolled in a different clinical trial.