The aim of this study is to evaluate the feasibility of collecting synchronised continuous temperature data using wearable devices and a continuous core temperature reference under real-world conditions. The study focuses on workflow execution, data continuity, secure retrieval, and time-alignment without diagnostic or therapeutic intent.

Continuous temperature monitoring in real-world and free-living settings is operationally challenging due to intermittent standard measurements and context-dependent variability. This limits the ability to evaluate the integrity and stability of continuous temperature time-series and to test end-to-end data collection workflows.

This feasibility study is conducted to determine whether synchronised continuous temperature data from wearable devices and an ingestible core temperature reference can be collected, time-aligned, and retrieved reliably with acceptable participant and staff burden. The study generates feasibility evidence on workflow performance and data stability to inform the design of a subsequent confirmatory clinical investigation.

Inclusion Criteria:

• Written informed consent obtained prior to any project-specific procedures.
• Age 18 years or older at enrolment.
• Able and willing to comply with project procedures, including capsule ingestion, continuous wearable use for around 48 hours, and adherence to study instructions.
• Able to swallow the ingestible temperature capsule without difficulty.
• No contraindication to ingestible thermometry as assessed by the investigator.

Exclusion Criteria:

General:

• Body weight < 36 kg.
• Women who are pregnant.
• Participation in another clinical investigation involving an investigational medicinal product or medical device within the 30 days preceding enrolment or previous enrolment in the current project.
• Enrolment of the Principal Investigator, project staff, their family members, employees, or other dependent persons.
• Inability to provide valid informed consent or significant language barrier preventing adequate understanding of procedures.

Implants & MRI:

• Presence of any active Implantable Medical Device (AIMD), including Pacemakers, Implantable Cardioverter Defibrillators (ICDs), Deep Brain Stimulation (DBS) devices, or Left Ventricular Assist Devices (LVADs).
• Requirement for MRI scanning during the seven days following the capsule intake.

Cognitive/Physical Status:

• Unconscious patients (prior to ingestion).
• Patients with special needs or disabilities preventing safe autonomous swallowing.

Gastrointestinal:

• Known history of dysphagia or gag reflex troubles.
• Previous gastrointestinal surgery resulting in bowel stenosis.
• Current or planned surgical procedures on the GI tract (esophagus, stomach, intestines).
• Zenker's diverticulum or felinization of the esophagus.
• Risk or history of intestinal obstruction, strictures, or diverticula.
• Hypomotility disorders (e.g., ileus).
• Inflammatory Bowel Diseases including Crohn's disease or Ulcerative Colitis.

Dermatological Exclusions (Rheo Vital+ Performance)

• Dermatological conditions, wounds, tattoos, oedema, inflammation, active venous access, or other impairments at the medial upper arm or axillary region that could interfere with correct placement or functioning of the wearable device.
• Excessive hair or concurrent devices that hinder correct sensor placement.
• Known allergy to plastics or latex.

Temperature Management:

• Active external heating or cooling (e.g., cooling blankets).
• Note: Use of pharmacological antipyretics (oral/IV) is permitted.

Further Medical Conditions:

• Currently existing acute back pain.
• Symptomatic herniated disc.

Adult participants (≥18 years) capable of providing informed consent and willing to comply with the project procedures, including ingestion of the capsule and continuous wearing of two wearable devices for around 48 hours until capsule excretion under free-living conditions.